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	$211.94	12.351%	$238.1167	$238.12	$238.10	$238.10
Purchase #2	$139.61	11.345%	$155.4488	$155.45	$155.45	$155.40
Purchase #3	$185.34	10.328%	$204.4819	$204.48	$204.50	$204.50
Purchase #4	$107.75	11.218%	$119.8374	$119.84	$119.85	$119.80
Purchase #5	$83.88	8.609%	$91.1012	$91.10	$91.10	$91.10
Purchase #6	$196.62	7.592%	$211.5474	$211.55	$211.55	$211.50
Purchase #7	$135.36	6.512%	$144.1746	$144.17	$144.15	$144.20
7 purchase totals =	$1,060.50		$1,164.7080	$1,164.71	$1,164.70	$1,164.60