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	$93.61	12.540%	$105.3487	$105.35	$105.35	$105.30
Purchase #2	$216.98	6.295%	$230.6389	$230.64	$230.65	$230.60
Purchase #3	$234.48	7.450%	$251.9488	$251.95	$251.95	$251.90
Purchase #4	$173.51	13.234%	$196.4723	$196.47	$196.45	$196.50
Purchase #5	$59.32	10.294%	$65.4264	$65.43	$65.45	$65.40
Purchase #6	$178.95	9.639%	$196.199	$196.20	$196.20	$196.20
Purchase #7	$179.79	4.394%	$187.69	$187.69	$187.70	$187.70
7 purchase totals =	$1,136.64		$1,233.7241	$1,233.73	$1,233.75	$1,233.60