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	$57.74	6.467%	$61.474	$61.47	$61.45	$61.50
Purchase #2	$89.35	9.345%	$97.6998	$97.70	$97.70	$97.70
Purchase #3	$126.62	7.517%	$136.138	$136.14	$136.15	$136.10
Purchase #4	$36.89	11.484%	$41.1264	$41.13	$41.15	$41.10
Purchase #5	$72.56	13.144%	$82.0973	$82.10	$82.10	$82.10
Purchase #6	$165.97	6.841%	$177.324	$177.32	$177.30	$177.30
Purchase #7	$98.91	13.123%	$111.89	$111.89	$111.90	$111.90
7 purchase totals =	$648.04		$707.7495	$707.75	$707.75	$707.70