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	$128.47	4.403%	$134.1265	$134.13	$134.15	$134.10
Purchase #2	$219.81	3.662%	$227.8594	$227.86	$227.85	$227.90
Purchase #3	$234.40	7.646%	$252.3222	$252.32	$252.30	$252.30
Purchase #4	$147.77	5.721%	$156.2239	$156.22	$156.20	$156.20
Purchase #5	$93.37	8.111%	$100.9432	$100.94	$100.95	$100.90
Purchase #6	$103.98	12.435%	$116.9099	$116.91	$116.90	$116.90
Purchase #7	$131.67	9.600%	$144.3103	$144.31	$144.30	$144.30
7 purchase totals =	$1,059.47		$1,132.6954	$1,132.69	$1,132.65	$1,132.60