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	$125.42	7.494%	$134.819	$134.82	$134.80	$134.80
Purchase #2	$198.57	11.840%	$222.0807	$222.08	$222.10	$222.10
Purchase #3	$175.53	3.701%	$182.0264	$182.03	$182.05	$182.00
Purchase #4	$98.35	7.600%	$105.8246	$105.82	$105.80	$105.80
Purchase #5	$216.29	6.330%	$229.9812	$229.98	$230.00	$230.00
Purchase #6	$11.38	7.853%	$12.2737	$12.27	$12.25	$12.30
Purchase #7	$149.88	13.766%	$170.5125	$170.51	$170.50	$170.50
7 purchase totals =	$975.42		$1,057.5181	$1,057.51	$1,057.50	$1,057.50