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	$131.89	7.167%	$141.3426	$141.34	$141.35	$141.30
Purchase #2	$85.91	3.228%	$88.6832	$88.68	$88.70	$88.70
Purchase #3	$5.41	12.433%	$6.0826	$6.08	$6.10	$6.10
Purchase #4	$66.98	4.607%	$70.0658	$70.07	$70.05	$70.10
Purchase #5	$38.39	11.115%	$42.657	$42.66	$42.65	$42.70
Purchase #6	$109.47	4.603%	$114.5089	$114.51	$114.50	$114.50
Purchase #7	$185.43	11.273%	$206.3335	$206.33	$206.35	$206.30
7 purchase totals =	$623.48		$669.6736	$669.67	$669.70	$669.70