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	$37.62	9.871%	$41.3335	$41.33	$41.35	$41.30
Purchase #2	$229.82	7.321%	$246.6451	$246.65	$246.65	$246.60
Purchase #3	$150.69	13.832%	$171.5334	$171.53	$171.55	$171.50
Purchase #4	$197.65	11.624%	$220.6248	$220.62	$220.60	$220.60
Purchase #5	$97.97	10.355%	$108.1148	$108.11	$108.10	$108.10
Purchase #6	$191.69	10.372%	$211.5721	$211.57	$211.55	$211.60
Purchase #7	$114.59	7.802%	$123.5303	$123.53	$123.55	$123.50
7 purchase totals =	$1,020.03		$1,123.3540	$1,123.34	$1,123.35	$1,123.20