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	$125.87	9.221%	$137.4765	$137.48	$137.50	$137.50
Purchase #2	$83.31	7.484%	$89.5449	$89.54	$89.55	$89.50
Purchase #3	$173.29	8.188%	$187.479	$187.48	$187.50	$187.50
Purchase #4	$104.27	7.428%	$112.0152	$112.02	$112.00	$112.00
Purchase #5	$124.60	5.664%	$131.6573	$131.66	$131.65	$131.70
Purchase #6	$114.82	4.821%	$120.3555	$120.36	$120.35	$120.40
Purchase #7	$155.42	12.606%	$175.0122	$175.01	$175.00	$175.00
7 purchase totals =	$881.58		$953.5406	$953.55	$953.55	$953.60