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	$74.68	10.427%	$82.4669	$82.47	$82.45	$82.50
Purchase #2	$133.29	13.756%	$151.6254	$151.63	$151.65	$151.60
Purchase #3	$233.56	4.375%	$243.7783	$243.78	$243.80	$243.80
Purchase #4	$62.66	4.146%	$65.2579	$65.26	$65.25	$65.30
Purchase #5	$189.67	3.398%	$196.115	$196.12	$196.10	$196.10
Purchase #6	$86.60	11.523%	$96.5789	$96.58	$96.60	$96.60
Purchase #7	$92.52	4.191%	$96.3975	$96.40	$96.40	$96.40
7 purchase totals =	$872.98		$932.2199	$932.24	$932.25	$932.30