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	$185.46	8.168%	$200.6084	$200.61	$200.60	$200.60
Purchase #2	$41.38	4.243%	$43.1358	$43.14	$43.15	$43.10
Purchase #3	$50.56	10.220%	$55.7272	$55.73	$55.75	$55.70
Purchase #4	$109.55	7.491%	$117.7564	$117.76	$117.75	$117.80
Purchase #5	$208.93	4.353%	$218.0247	$218.02	$218.00	$218.00
Purchase #6	$149.50	5.719%	$158.0499	$158.05	$158.05	$158.00
Purchase #7	$56.45	10.406%	$62.3242	$62.32	$62.30	$62.30
7 purchase totals =	$801.83		$855.6266	$855.63	$855.60	$855.50