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	$151.29	4.745%	$158.4687	$158.47	$158.45	$158.50
Purchase #2	$193.51	3.723%	$200.7144	$200.71	$200.70	$200.70
Purchase #3	$195.67	3.872%	$203.2463	$203.25	$203.25	$203.20
Purchase #4	$115.74	6.800%	$123.6103	$123.61	$123.60	$123.60
Purchase #5	$53.48	10.771%	$59.2403	$59.24	$59.25	$59.20
Purchase #6	$124.42	13.301%	$140.9691	$140.97	$140.95	$141.00
Purchase #7	$52.58	7.169%	$56.3495	$56.35	$56.35	$56.30
7 purchase totals =	$886.69		$942.5986	$942.60	$942.55	$942.50