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	$194.88	12.707%	$219.6434	$219.64	$219.65	$219.60
Purchase #2	$62.42	3.413%	$64.5504	$64.55	$64.55	$64.60
Purchase #3	$37.48	13.321%	$42.4727	$42.47	$42.45	$42.50
Purchase #4	$239.69	4.393%	$250.2196	$250.22	$250.20	$250.20
Purchase #5	$201.92	3.741%	$209.4738	$209.47	$209.45	$209.50
Purchase #6	$233.33	4.373%	$243.5335	$243.53	$243.55	$243.50
Purchase #7	$245.48	4.191%	$255.7681	$255.77	$255.75	$255.80
7 purchase totals =	$1,215.20		$1,285.6615	$1,285.65	$1,285.60	$1,285.70