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	$109.30	12.595%	$123.0663	$123.07	$123.05	$123.10
Purchase #2	$186.61	5.731%	$197.3046	$197.30	$197.30	$197.30
Purchase #3	$67.25	5.633%	$71.0382	$71.04	$71.05	$71.00
Purchase #4	$142.84	8.550%	$155.0528	$155.05	$155.05	$155.10
Purchase #5	$6.55	8.870%	$7.131	$7.13	$7.15	$7.10
Purchase #6	$54.37	8.781%	$59.1442	$59.14	$59.15	$59.10
Purchase #7	$112.87	7.105%	$120.8894	$120.89	$120.90	$120.90
7 purchase totals =	$679.79		$733.6265	$733.62	$733.65	$733.60