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	$49.36	11.244%	$54.91	$54.91	$54.90	$54.90
Purchase #2	$58.73	10.452%	$64.8685	$64.87	$64.85	$64.90
Purchase #3	$7.53	9.190%	$8.222	$8.22	$8.20	$8.20
Purchase #4	$67.89	7.390%	$72.9071	$72.91	$72.90	$72.90
Purchase #5	$245.53	5.353%	$258.6732	$258.67	$258.65	$258.70
Purchase #6	$190.81	4.773%	$199.9174	$199.92	$199.90	$199.90
Purchase #7	$129.29	8.618%	$140.4322	$140.43	$140.45	$140.40
7 purchase totals =	$749.14		$799.9304	$799.93	$799.85	$799.90