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	$98.39	13.220%	$111.3972	$111.40	$111.40	$111.40
Purchase #2	$99.89	5.512%	$105.3959	$105.40	$105.40	$105.40
Purchase #3	$124.29	9.726%	$136.3784	$136.38	$136.40	$136.40
Purchase #4	$49.87	4.544%	$52.1361	$52.14	$52.15	$52.10
Purchase #5	$175.94	8.667%	$191.1887	$191.19	$191.20	$191.20
Purchase #6	$247.86	8.642%	$269.2801	$269.28	$269.30	$269.30
Purchase #7	$58.30	13.820%	$66.3571	$66.36	$66.35	$66.40
7 purchase totals =	$854.54		$932.1335	$932.15	$932.20	$932.20