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	$227.72	5.857%	$241.0576	$241.06	$241.05	$241.10
Purchase #2	$86.79	11.211%	$96.52	$96.52	$96.50	$96.50
Purchase #3	$52.56	7.487%	$56.4952	$56.50	$56.50	$56.50
Purchase #4	$180.46	3.674%	$187.0901	$187.09	$187.10	$187.10
Purchase #5	$231.65	4.204%	$241.3886	$241.39	$241.40	$241.40
Purchase #6	$174.44	13.779%	$198.4761	$198.48	$198.50	$198.50
Purchase #7	$242.81	5.219%	$255.4823	$255.48	$255.50	$255.50
7 purchase totals =	$1,196.43		$1,276.5099	$1,276.52	$1,276.55	$1,276.60