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	$85.98	3.698%	$89.1595	$89.16	$89.15	$89.20
Purchase #2	$109.48	8.637%	$118.9358	$118.94	$118.95	$118.90
Purchase #3	$67.93	13.218%	$76.909	$76.91	$76.90	$76.90
Purchase #4	$74.90	9.772%	$82.2192	$82.22	$82.20	$82.20
Purchase #5	$185.50	10.139%	$204.3078	$204.31	$204.30	$204.30
Purchase #6	$222.82	6.148%	$236.519	$236.52	$236.50	$236.50
Purchase #7	$108.65	7.560%	$116.8639	$116.86	$116.85	$116.90
7 purchase totals =	$855.26		$924.9142	$924.92	$924.85	$924.90