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	$181.97	8.167%	$196.8315	$196.83	$196.85	$196.80
Purchase #2	$244.39	9.503%	$267.6144	$267.61	$267.60	$267.60
Purchase #3	$131.98	10.155%	$145.3826	$145.38	$145.40	$145.40
Purchase #4	$221.59	9.832%	$243.3767	$243.38	$243.40	$243.40
Purchase #5	$47.91	12.528%	$53.9122	$53.91	$53.90	$53.90
Purchase #6	$19.32	12.422%	$21.7199	$21.72	$21.70	$21.70
Purchase #7	$193.66	13.162%	$219.1495	$219.15	$219.15	$219.10
7 purchase totals =	$1,040.82		$1,147.9868	$1,147.98	$1,148.00	$1,147.90