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	$108.29	7.427%	$116.3327	$116.33	$116.35	$116.30
Purchase #2	$46.72	11.658%	$52.1666	$52.17	$52.15	$52.20
Purchase #3	$87.81	4.595%	$91.8449	$91.84	$91.85	$91.80
Purchase #4	$105.26	3.830%	$109.2915	$109.29	$109.30	$109.30
Purchase #5	$175.44	11.760%	$196.0717	$196.07	$196.05	$196.10
Purchase #6	$32.96	8.675%	$35.8193	$35.82	$35.80	$35.80
Purchase #7	$71.35	3.412%	$73.7845	$73.78	$73.80	$73.80
7 purchase totals =	$627.83		$675.3112	$675.30	$675.30	$675.30