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	$63.79	10.486%	$70.479	$70.48	$70.50	$70.50
Purchase #2	$174.85	13.177%	$197.89	$197.89	$197.90	$197.90
Purchase #3	$160.80	11.515%	$179.3161	$179.32	$179.30	$179.30
Purchase #4	$227.73	6.782%	$243.1746	$243.17	$243.15	$243.20
Purchase #5	$65.51	9.301%	$71.6031	$71.60	$71.60	$71.60
Purchase #6	$123.29	13.202%	$139.5667	$139.57	$139.55	$139.60
Purchase #7	$111.94	11.391%	$124.6911	$124.69	$124.70	$124.70
7 purchase totals =	$927.91		$1,026.7206	$1,026.72	$1,026.70	$1,026.80