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	$232.68	13.524%	$264.1476	$264.15	$264.15	$264.10
Purchase #2	$57.71	3.742%	$59.8695	$59.87	$59.85	$59.90
Purchase #3	$50.97	4.753%	$53.3926	$53.39	$53.40	$53.40
Purchase #4	$169.78	7.681%	$182.8208	$182.82	$182.80	$182.80
Purchase #5	$62.39	5.266%	$65.6755	$65.68	$65.70	$65.70
Purchase #6	$91.27	7.258%	$97.8944	$97.89	$97.90	$97.90
Purchase #7	$15.47	9.780%	$16.983	$16.98	$17.00	$17.00
7 purchase totals =	$680.27		$740.7834	$740.78	$740.80	$740.80