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	$161.61	4.267%	$168.5059	$168.51	$168.50	$168.50
Purchase #2	$191.94	4.220%	$200.0399	$200.04	$200.05	$200.00
Purchase #3	$231.51	10.375%	$255.5292	$255.53	$255.55	$255.50
Purchase #4	$53.34	13.786%	$60.6935	$60.69	$60.70	$60.70
Purchase #5	$197.42	6.346%	$209.9483	$209.95	$209.95	$209.90
Purchase #6	$42.61	13.191%	$48.2307	$48.23	$48.25	$48.20
Purchase #7	$23.75	7.593%	$25.5533	$25.55	$25.55	$25.60
7 purchase totals =	$902.18		$968.5008	$968.50	$968.55	$968.40