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	$41.51	9.545%	$45.4721	$45.47	$45.45	$45.50
Purchase #2	$89.61	6.421%	$95.3639	$95.36	$95.35	$95.40
Purchase #3	$35.75	6.568%	$38.0981	$38.10	$38.10	$38.10
Purchase #4	$58.37	5.632%	$61.6574	$61.66	$61.65	$61.70
Purchase #5	$36.32	3.591%	$37.6243	$37.62	$37.60	$37.60
Purchase #6	$74.84	10.753%	$82.8875	$82.89	$82.90	$82.90
Purchase #7	$10.40	5.223%	$10.9432	$10.94	$10.95	$10.90
7 purchase totals =	$346.80		$372.0465	$372.04	$372.00	$372.10