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	$236.27	4.353%	$246.5548	$246.55	$246.55	$246.60
Purchase #2	$182.62	7.829%	$196.9173	$196.92	$196.90	$196.90
Purchase #3	$139.29	9.631%	$152.705	$152.71	$152.70	$152.70
Purchase #4	$94.65	4.459%	$98.8704	$98.87	$98.85	$98.90
Purchase #5	$169.87	4.829%	$178.073	$178.07	$178.05	$178.10
Purchase #6	$84.63	9.471%	$92.6453	$92.65	$92.65	$92.60
Purchase #7	$39.37	13.340%	$44.622	$44.62	$44.60	$44.60
7 purchase totals =	$946.70		$1,010.3878	$1,010.39	$1,010.30	$1,010.40