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	$89.80	8.182%	$97.1474	$97.15	$97.15	$97.10
Purchase #2	$240.59	6.193%	$255.4897	$255.49	$255.50	$255.50
Purchase #3	$44.67	5.790%	$47.2564	$47.26	$47.25	$47.30
Purchase #4	$141.79	4.604%	$148.318	$148.32	$148.30	$148.30
Purchase #5	$77.33	6.530%	$82.3796	$82.38	$82.40	$82.40
Purchase #6	$129.83	12.283%	$145.777	$145.78	$145.80	$145.80
Purchase #7	$222.96	9.208%	$243.4902	$243.49	$243.50	$243.50
7 purchase totals =	$946.97		$1,019.8583	$1,019.87	$1,019.90	$1,019.90