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	$223.72	13.785%	$254.5598	$254.56	$254.55	$254.60
Purchase #2	$50.89	3.308%	$52.5734	$52.57	$52.55	$52.60
Purchase #3	$205.99	12.748%	$232.2496	$232.25	$232.25	$232.20
Purchase #4	$106.85	4.179%	$111.3153	$111.32	$111.30	$111.30
Purchase #5	$116.81	9.787%	$128.2422	$128.24	$128.25	$128.20
Purchase #6	$167.40	13.281%	$189.6324	$189.63	$189.65	$189.60
Purchase #7	$52.55	4.523%	$54.9268	$54.93	$54.95	$54.90
7 purchase totals =	$924.21		$1,023.4995	$1,023.50	$1,023.50	$1,023.40