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	$225.54	7.315%	$242.0383	$242.04	$242.05	$242.00
Purchase #2	$120.69	7.812%	$130.1183	$130.12	$130.10	$130.10
Purchase #3	$205.91	11.637%	$229.8717	$229.87	$229.85	$229.90
Purchase #4	$88.61	7.570%	$95.3178	$95.32	$95.30	$95.30
Purchase #5	$149.31	10.191%	$164.5262	$164.53	$164.55	$164.50
Purchase #6	$121.89	8.414%	$132.1458	$132.15	$132.15	$132.10
Purchase #7	$36.36	11.792%	$40.6476	$40.65	$40.65	$40.60
7 purchase totals =	$948.31		$1,034.6657	$1,034.68	$1,034.65	$1,034.50