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	$32.61	10.112%	$35.9075	$35.91	$35.90	$35.90
Purchase #2	$116.74	10.412%	$128.895	$128.90	$128.90	$128.90
Purchase #3	$99.33	12.555%	$111.8009	$111.80	$111.80	$111.80
Purchase #4	$236.50	9.580%	$259.1567	$259.16	$259.15	$259.20
Purchase #5	$116.68	3.444%	$120.6985	$120.70	$120.70	$120.70
Purchase #6	$175.84	10.818%	$194.8624	$194.86	$194.85	$194.90
Purchase #7	$244.33	4.132%	$254.4257	$254.43	$254.45	$254.40
7 purchase totals =	$1,022.03		$1,105.7467	$1,105.76	$1,105.75	$1,105.80