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	$152.54	3.690%	$158.1687	$158.17	$158.15	$158.20
Purchase #2	$210.94	11.325%	$234.829	$234.83	$234.85	$234.80
Purchase #3	$171.89	11.443%	$191.5594	$191.56	$191.55	$191.60
Purchase #4	$168.54	13.771%	$191.7496	$191.75	$191.75	$191.70
Purchase #5	$206.89	12.404%	$232.5526	$232.55	$232.55	$232.60
Purchase #6	$196.59	3.635%	$203.736	$203.74	$203.75	$203.70
Purchase #7	$74.82	10.137%	$82.4045	$82.40	$82.40	$82.40
7 purchase totals =	$1,182.21		$1,294.9998	$1,295.00	$1,295.00	$1,295.00