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	$235.94	8.328%	$255.5891	$255.59	$255.60	$255.60
Purchase #2	$59.46	13.580%	$67.5347	$67.53	$67.55	$67.50
Purchase #3	$79.33	5.626%	$83.7931	$83.79	$83.80	$83.80
Purchase #4	$246.93	7.488%	$265.4201	$265.42	$265.40	$265.40
Purchase #5	$127.45	13.719%	$144.9349	$144.93	$144.95	$144.90
Purchase #6	$28.90	8.247%	$31.2834	$31.28	$31.30	$31.30
Purchase #7	$195.73	13.468%	$222.0909	$222.09	$222.10	$222.10
7 purchase totals =	$973.74		$1,070.6462	$1,070.63	$1,070.70	$1,070.60