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	$195.54	8.368%	$211.9028	$211.90	$211.90	$211.90
Purchase #2	$33.59	13.455%	$38.1095	$38.11	$38.10	$38.10
Purchase #3	$146.56	13.720%	$166.668	$166.67	$166.65	$166.70
Purchase #4	$106.93	9.774%	$117.3813	$117.38	$117.40	$117.40
Purchase #5	$52.82	10.708%	$58.476	$58.48	$58.50	$58.50
Purchase #6	$193.31	13.522%	$219.4494	$219.45	$219.45	$219.40
Purchase #7	$187.80	4.397%	$196.0576	$196.06	$196.05	$196.10
7 purchase totals =	$916.55		$1,008.0446	$1,008.05	$1,008.05	$1,008.10