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	$184.61	5.862%	$195.4318	$195.43	$195.45	$195.40
Purchase #2	$169.41	9.704%	$185.8495	$185.85	$185.85	$185.80
Purchase #3	$99.80	5.672%	$105.4607	$105.46	$105.45	$105.50
Purchase #4	$83.55	6.171%	$88.7059	$88.71	$88.70	$88.70
Purchase #5	$69.90	9.229%	$76.3511	$76.35	$76.35	$76.40
Purchase #6	$149.48	6.342%	$158.96	$158.96	$158.95	$159.00
Purchase #7	$70.48	3.758%	$73.1286	$73.13	$73.15	$73.10
7 purchase totals =	$827.23		$883.8876	$883.89	$883.90	$883.90