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	$81.43	13.625%	$92.5248	$92.52	$92.50	$92.50
Purchase #2	$82.73	8.709%	$89.935	$89.94	$89.95	$89.90
Purchase #3	$34.61	6.369%	$36.8143	$36.81	$36.80	$36.80
Purchase #4	$18.67	5.280%	$19.6558	$19.66	$19.65	$19.70
Purchase #5	$90.51	7.482%	$97.282	$97.28	$97.30	$97.30
Purchase #6	$36.90	12.790%	$41.6195	$41.62	$41.60	$41.60
Purchase #7	$70.80	10.479%	$78.2191	$78.22	$78.20	$78.20
7 purchase totals =	$415.65		$456.0505	$456.05	$456.00	$456.00