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	$198.96	12.481%	$223.7922	$223.79	$223.80	$223.80
Purchase #2	$196.44	9.774%	$215.64	$215.64	$215.65	$215.60
Purchase #3	$103.66	7.707%	$111.6491	$111.65	$111.65	$111.60
Purchase #4	$93.60	9.130%	$102.1457	$102.15	$102.15	$102.10
Purchase #5	$183.67	5.742%	$194.2163	$194.22	$194.20	$194.20
Purchase #6	$54.35	10.562%	$60.0904	$60.09	$60.10	$60.10
Purchase #7	$217.66	11.806%	$243.3569	$243.36	$243.35	$243.40
7 purchase totals =	$1,048.34		$1,150.8906	$1,150.90	$1,150.90	$1,150.80