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	$63.46	10.503%	$70.1252	$70.13	$70.15	$70.10
Purchase #2	$64.58	9.682%	$70.8326	$70.83	$70.85	$70.80
Purchase #3	$86.73	3.790%	$90.0171	$90.02	$90.00	$90.00
Purchase #4	$216.86	7.693%	$233.543	$233.54	$233.55	$233.50
Purchase #5	$182.36	11.165%	$202.7205	$202.72	$202.70	$202.70
Purchase #6	$217.48	12.512%	$244.6911	$244.69	$244.70	$244.70
Purchase #7	$146.30	6.287%	$155.4979	$155.50	$155.50	$155.50
7 purchase totals =	$977.77		$1,067.4274	$1,067.43	$1,067.45	$1,067.30