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	$144.56	4.560%	$151.1519	$151.15	$151.15	$151.20
Purchase #2	$10.86	10.737%	$12.026	$12.03	$12.05	$12.00
Purchase #3	$88.52	12.554%	$99.6328	$99.63	$99.65	$99.60
Purchase #4	$101.83	8.561%	$110.5477	$110.55	$110.55	$110.50
Purchase #5	$148.70	9.494%	$162.8176	$162.82	$162.80	$162.80
Purchase #6	$79.48	5.552%	$83.8927	$83.89	$83.90	$83.90
Purchase #7	$217.36	13.643%	$247.0144	$247.01	$247.00	$247.00
7 purchase totals =	$791.31		$867.0831	$867.08	$867.10	$867.00