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	$155.57	12.706%	$175.3367	$175.34	$175.35	$175.30
Purchase #2	$146.60	13.450%	$166.3177	$166.32	$166.30	$166.30
Purchase #3	$36.97	5.185%	$38.8869	$38.89	$38.90	$38.90
Purchase #4	$33.43	9.377%	$36.5647	$36.56	$36.55	$36.60
Purchase #5	$175.34	11.773%	$195.9828	$195.98	$196.00	$196.00
Purchase #6	$23.45	4.859%	$24.5894	$24.59	$24.60	$24.60
Purchase #7	$174.72	9.114%	$190.644	$190.64	$190.65	$190.60
7 purchase totals =	$746.08		$828.3222	$828.32	$828.35	$828.30