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	$171.67	7.540%	$184.6139	$184.61	$184.60	$184.60
Purchase #2	$151.70	8.721%	$164.9298	$164.93	$164.95	$164.90
Purchase #3	$96.54	12.283%	$108.398	$108.40	$108.40	$108.40
Purchase #4	$116.46	13.198%	$131.8304	$131.83	$131.85	$131.80
Purchase #5	$143.52	6.142%	$152.335	$152.34	$152.35	$152.30
Purchase #6	$102.78	7.471%	$110.4587	$110.46	$110.45	$110.50
Purchase #7	$247.78	10.525%	$273.8588	$273.86	$273.85	$273.90
7 purchase totals =	$1,030.45		$1,126.4246	$1,126.43	$1,126.45	$1,126.40