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	$45.97	10.278%	$50.6948	$50.69	$50.70	$50.70
Purchase #2	$134.38	10.838%	$148.9441	$148.94	$148.95	$148.90
Purchase #3	$32.57	13.289%	$36.8982	$36.90	$36.90	$36.90
Purchase #4	$191.94	10.317%	$211.7424	$211.74	$211.75	$211.70
Purchase #5	$66.50	6.855%	$71.0586	$71.06	$71.05	$71.10
Purchase #6	$95.88	3.751%	$99.4765	$99.48	$99.50	$99.50
Purchase #7	$116.39	9.294%	$127.2073	$127.21	$127.20	$127.20
7 purchase totals =	$683.63		$746.0219	$746.02	$746.05	$746.00