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	$188.98	10.147%	$208.1558	$208.16	$208.15	$208.20
Purchase #2	$230.91	3.307%	$238.5462	$238.55	$238.55	$238.50
Purchase #3	$84.63	8.181%	$91.5536	$91.55	$91.55	$91.60
Purchase #4	$130.67	11.355%	$145.5076	$145.51	$145.50	$145.50
Purchase #5	$112.63	10.174%	$124.089	$124.09	$124.10	$124.10
Purchase #6	$6.93	8.575%	$7.5242	$7.52	$7.50	$7.50
Purchase #7	$206.95	13.626%	$235.149	$235.15	$235.15	$235.10
7 purchase totals =	$961.70		$1,050.5254	$1,050.53	$1,050.50	$1,050.50