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	$11.75	5.309%	$12.3738	$12.37	$12.35	$12.40
Purchase #2	$143.98	6.148%	$152.8319	$152.83	$152.85	$152.80
Purchase #3	$83.28	9.647%	$91.314	$91.31	$91.30	$91.30
Purchase #4	$111.91	8.594%	$121.5275	$121.53	$121.55	$121.50
Purchase #5	$171.58	8.109%	$185.4934	$185.49	$185.50	$185.50
Purchase #6	$208.42	10.197%	$229.6726	$229.67	$229.65	$229.70
Purchase #7	$218.49	6.369%	$232.4056	$232.41	$232.40	$232.40
7 purchase totals =	$949.41		$1,025.6188	$1,025.61	$1,025.60	$1,025.60