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	$152.76	8.393%	$165.5811	$165.58	$165.60	$165.60
Purchase #2	$196.50	6.182%	$208.6476	$208.65	$208.65	$208.60
Purchase #3	$55.61	12.399%	$62.5051	$62.51	$62.50	$62.50
Purchase #4	$131.61	3.114%	$135.7083	$135.71	$135.70	$135.70
Purchase #5	$120.64	6.408%	$128.3706	$128.37	$128.35	$128.40
Purchase #6	$245.67	5.481%	$259.1352	$259.14	$259.15	$259.10
Purchase #7	$80.86	6.188%	$85.8636	$85.86	$85.85	$85.90
7 purchase totals =	$983.65		$1,045.8115	$1,045.82	$1,045.80	$1,045.80