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	$225.81	11.357%	$251.4552	$251.46	$251.45	$251.50
Purchase #2	$116.46	11.428%	$129.769	$129.77	$129.75	$129.80
Purchase #3	$32.72	3.528%	$33.8744	$33.87	$33.85	$33.90
Purchase #4	$246.35	4.285%	$256.9061	$256.91	$256.90	$256.90
Purchase #5	$244.30	9.185%	$266.739	$266.74	$266.75	$266.70
Purchase #6	$93.36	6.587%	$99.5096	$99.51	$99.50	$99.50
Purchase #7	$97.47	12.342%	$109.4997	$109.50	$109.50	$109.50
7 purchase totals =	$1,056.47		$1,147.7530	$1,147.76	$1,147.70	$1,147.80