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	$100.75	10.375%	$111.2028	$111.20	$111.20	$111.20
Purchase #2	$140.72	8.545%	$152.7445	$152.74	$152.75	$152.70
Purchase #3	$202.49	13.360%	$229.5427	$229.54	$229.55	$229.50
Purchase #4	$245.31	13.865%	$279.3222	$279.32	$279.30	$279.30
Purchase #5	$87.65	11.864%	$98.0488	$98.05	$98.05	$98.00
Purchase #6	$138.33	10.440%	$152.7717	$152.77	$152.75	$152.80
Purchase #7	$10.73	5.205%	$11.2885	$11.29	$11.30	$11.30
7 purchase totals =	$925.98		$1,034.9212	$1,034.91	$1,034.90	$1,034.80