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	$52.57	5.181%	$55.2937	$55.29	$55.30	$55.30
Purchase #2	$20.90	6.757%	$22.3122	$22.31	$22.30	$22.30
Purchase #3	$242.27	5.593%	$255.8202	$255.82	$255.80	$255.80
Purchase #4	$61.33	10.605%	$67.834	$67.83	$67.85	$67.80
Purchase #5	$30.96	6.528%	$32.9811	$32.98	$33.00	$33.00
Purchase #6	$149.93	11.312%	$166.8901	$166.89	$166.90	$166.90
Purchase #7	$78.53	11.137%	$87.2759	$87.28	$87.30	$87.30
7 purchase totals =	$636.49		$688.4072	$688.40	$688.45	$688.40