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	$226.70	6.434%	$241.2859	$241.29	$241.30	$241.30
Purchase #2	$155.79	11.445%	$173.6202	$173.62	$173.60	$173.60
Purchase #3	$40.85	6.139%	$43.3578	$43.36	$43.35	$43.40
Purchase #4	$247.66	13.188%	$280.3214	$280.32	$280.30	$280.30
Purchase #5	$71.74	6.623%	$76.4913	$76.49	$76.50	$76.50
Purchase #6	$250.72	5.418%	$264.304	$264.30	$264.30	$264.30
Purchase #7	$59.50	3.380%	$61.5111	$61.51	$61.50	$61.50
7 purchase totals =	$1,052.96		$1,140.8917	$1,140.89	$1,140.85	$1,140.90