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	$90.75	4.538%	$94.8682	$94.87	$94.85	$94.90
Purchase #2	$165.29	5.552%	$174.4669	$174.47	$174.45	$174.50
Purchase #3	$103.85	7.603%	$111.7457	$111.75	$111.75	$111.70
Purchase #4	$28.83	4.801%	$30.2141	$30.21	$30.20	$30.20
Purchase #5	$100.94	5.352%	$106.3423	$106.34	$106.35	$106.30
Purchase #6	$109.31	10.236%	$120.499	$120.50	$120.50	$120.50
Purchase #7	$142.69	8.517%	$154.8429	$154.84	$154.85	$154.80
7 purchase totals =	$741.66		$792.9791	$792.98	$792.95	$792.90