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	$77.79	13.500%	$88.2917	$88.29	$88.30	$88.30
Purchase #2	$47.50	13.850%	$54.0788	$54.08	$54.10	$54.10
Purchase #3	$221.76	9.666%	$243.1953	$243.20	$243.20	$243.20
Purchase #4	$61.83	9.394%	$67.6383	$67.64	$67.65	$67.60
Purchase #5	$242.38	11.748%	$270.8548	$270.85	$270.85	$270.90
Purchase #6	$59.83	13.224%	$67.7419	$67.74	$67.75	$67.70
Purchase #7	$242.88	10.819%	$269.1572	$269.16	$269.15	$269.20
7 purchase totals =	$953.97		$1,060.9580	$1,060.96	$1,061.00	$1,061.00