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	$148.38	4.751%	$155.4295	$155.43	$155.45	$155.40
Purchase #2	$98.46	6.146%	$104.5114	$104.51	$104.50	$104.50
Purchase #3	$201.42	6.103%	$213.7127	$213.71	$213.70	$213.70
Purchase #4	$152.26	10.355%	$168.0265	$168.03	$168.05	$168.00
Purchase #5	$81.41	8.769%	$88.5488	$88.55	$88.55	$88.50
Purchase #6	$175.70	3.277%	$181.4577	$181.46	$181.45	$181.50
Purchase #7	$101.59	7.118%	$108.8212	$108.82	$108.80	$108.80
7 purchase totals =	$959.22		$1,020.5078	$1,020.51	$1,020.50	$1,020.40