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	$153.52	12.428%	$172.5995	$172.60	$172.60	$172.60
Purchase #2	$229.80	6.349%	$244.39	$244.39	$244.40	$244.40
Purchase #3	$149.50	13.392%	$169.521	$169.52	$169.50	$169.50
Purchase #4	$52.70	7.703%	$56.7595	$56.76	$56.75	$56.80
Purchase #5	$209.94	13.585%	$238.4603	$238.46	$238.45	$238.50
Purchase #6	$168.60	10.672%	$186.593	$186.59	$186.60	$186.60
Purchase #7	$73.48	13.651%	$83.5108	$83.51	$83.50	$83.50
7 purchase totals =	$1,037.54		$1,151.8341	$1,151.83	$1,151.80	$1,151.90