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	$37.45	11.319%	$41.689	$41.69	$41.70	$41.70
Purchase #2	$122.28	13.870%	$139.2402	$139.24	$139.25	$139.20
Purchase #3	$249.25	12.859%	$281.3011	$281.30	$281.30	$281.30
Purchase #4	$157.90	4.746%	$165.3939	$165.39	$165.40	$165.40
Purchase #5	$167.64	10.431%	$185.1265	$185.13	$185.15	$185.10
Purchase #6	$26.27	10.166%	$28.9406	$28.94	$28.95	$28.90
Purchase #7	$201.49	3.585%	$208.7134	$208.71	$208.70	$208.70
7 purchase totals =	$962.28		$1,050.4047	$1,050.40	$1,050.45	$1,050.30