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	$93.56	4.842%	$98.0902	$98.09	$98.10	$98.10
Purchase #2	$98.51	13.768%	$112.0729	$112.07	$112.05	$112.10
Purchase #3	$55.58	13.196%	$62.9143	$62.91	$62.90	$62.90
Purchase #4	$160.26	3.689%	$166.172	$166.17	$166.15	$166.20
Purchase #5	$62.44	3.333%	$64.5211	$64.52	$64.50	$64.50
Purchase #6	$14.37	4.438%	$15.0077	$15.01	$15.00	$15.00
Purchase #7	$143.33	6.581%	$152.7625	$152.76	$152.75	$152.80
7 purchase totals =	$628.05		$671.5407	$671.53	$671.45	$671.60