Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$175.78	4.173%	$183.1153	$183.12	$183.10	$183.10
Purchase #2	$226.70	3.456%	$234.5348	$234.53	$234.55	$234.50
Purchase #3	$243.81	11.231%	$271.1923	$271.19	$271.20	$271.20
Purchase #4	$171.99	11.238%	$191.3182	$191.32	$191.30	$191.30
Purchase #5	$247.73	13.404%	$280.9357	$280.94	$280.95	$280.90
Purchase #6	$102.63	8.461%	$111.3135	$111.31	$111.30	$111.30
Purchase #7	$235.67	10.272%	$259.878	$259.88	$259.90	$259.90
7 purchase totals =	$1,404.31		$1,532.2878	$1,532.29	$1,532.30	$1,532.20