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	$146.61	12.208%	$164.5081	$164.51	$164.50	$164.50
Purchase #2	$111.78	10.353%	$123.3526	$123.35	$123.35	$123.40
Purchase #3	$236.92	5.753%	$250.55	$250.55	$250.55	$250.60
Purchase #4	$164.69	6.675%	$175.6831	$175.68	$175.70	$175.70
Purchase #5	$213.79	6.236%	$227.1219	$227.12	$227.10	$227.10
Purchase #6	$80.35	12.560%	$90.442	$90.44	$90.45	$90.40
Purchase #7	$113.28	6.675%	$120.8414	$120.84	$120.85	$120.80
7 purchase totals =	$1,067.42		$1,152.4991	$1,152.49	$1,152.50	$1,152.50