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	$236.56	12.136%	$265.2689	$265.27	$265.25	$265.30
Purchase #2	$35.76	5.634%	$37.7747	$37.77	$37.75	$37.80
Purchase #3	$100.86	3.257%	$104.145	$104.15	$104.15	$104.10
Purchase #4	$222.76	9.310%	$243.499	$243.50	$243.50	$243.50
Purchase #5	$55.83	10.424%	$61.6497	$61.65	$61.65	$61.60
Purchase #6	$243.31	7.850%	$262.4098	$262.41	$262.40	$262.40
Purchase #7	$121.76	13.407%	$138.0844	$138.08	$138.10	$138.10
7 purchase totals =	$1,016.84		$1,112.8315	$1,112.83	$1,112.80	$1,112.80