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	$41.72	12.238%	$46.8257	$46.83	$46.85	$46.80
Purchase #2	$78.82	3.824%	$81.8341	$81.83	$81.85	$81.80
Purchase #3	$149.86	10.450%	$165.5204	$165.52	$165.50	$165.50
Purchase #4	$60.72	3.472%	$62.8282	$62.83	$62.85	$62.80
Purchase #5	$236.47	5.860%	$250.3271	$250.33	$250.35	$250.30
Purchase #6	$208.65	8.822%	$227.0571	$227.06	$227.05	$227.10
Purchase #7	$237.79	13.471%	$269.8227	$269.82	$269.80	$269.80
7 purchase totals =	$1,014.03		$1,104.2153	$1,104.22	$1,104.25	$1,104.10