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	$6.86	9.250%	$7.4946	$7.49	$7.50	$7.50
Purchase #2	$189.49	12.774%	$213.6955	$213.70	$213.70	$213.70
Purchase #3	$50.32	6.123%	$53.4011	$53.40	$53.40	$53.40
Purchase #4	$227.42	10.638%	$251.6129	$251.61	$251.60	$251.60
Purchase #5	$217.86	8.706%	$236.8269	$236.83	$236.85	$236.80
Purchase #6	$33.40	13.445%	$37.8906	$37.89	$37.90	$37.90
Purchase #7	$211.90	4.348%	$221.1134	$221.11	$221.10	$221.10
7 purchase totals =	$937.25		$1,022.0350	$1,022.03	$1,022.05	$1,022.00