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	$67.86	7.365%	$72.8579	$72.86	$72.85	$72.90
Purchase #2	$194.32	11.602%	$216.865	$216.87	$216.85	$216.90
Purchase #3	$153.99	8.871%	$167.6505	$167.65	$167.65	$167.70
Purchase #4	$135.40	6.459%	$144.1455	$144.15	$144.15	$144.10
Purchase #5	$89.73	6.191%	$95.2852	$95.29	$95.30	$95.30
Purchase #6	$231.62	11.451%	$258.1428	$258.14	$258.15	$258.10
Purchase #7	$6.47	7.636%	$6.964	$6.96	$6.95	$7.00
7 purchase totals =	$879.39		$961.9109	$961.92	$961.90	$962.00