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	$147.90	13.143%	$167.3385	$167.34	$167.35	$167.30
Purchase #2	$165.31	8.443%	$179.2671	$179.27	$179.25	$179.30
Purchase #3	$213.55	10.389%	$235.7357	$235.74	$235.75	$235.70
Purchase #4	$120.55	6.630%	$128.5425	$128.54	$128.55	$128.50
Purchase #5	$86.76	4.485%	$90.6512	$90.65	$90.65	$90.70
Purchase #6	$84.59	10.834%	$93.7545	$93.75	$93.75	$93.80
Purchase #7	$224.86	11.694%	$251.1551	$251.16	$251.15	$251.20
7 purchase totals =	$1,043.52		$1,146.4446	$1,146.45	$1,146.45	$1,146.50