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	$54.56	4.197%	$56.8499	$56.85	$56.85	$56.80
Purchase #2	$115.56	7.684%	$124.4396	$124.44	$124.45	$124.40
Purchase #3	$91.62	13.416%	$103.9117	$103.91	$103.90	$103.90
Purchase #4	$25.56	6.488%	$27.2183	$27.22	$27.20	$27.20
Purchase #5	$77.70	13.387%	$88.1017	$88.10	$88.10	$88.10
Purchase #6	$54.87	8.452%	$59.5076	$59.51	$59.50	$59.50
Purchase #7	$221.96	4.404%	$231.7351	$231.74	$231.75	$231.70
7 purchase totals =	$641.83		$691.7639	$691.77	$691.75	$691.60