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	$233.57	4.858%	$244.9168	$244.92	$244.90	$244.90
Purchase #2	$106.37	11.144%	$118.2239	$118.22	$118.20	$118.20
Purchase #3	$231.27	6.678%	$246.7142	$246.71	$246.70	$246.70
Purchase #4	$164.43	4.251%	$171.4199	$171.42	$171.40	$171.40
Purchase #5	$111.59	10.533%	$123.3438	$123.34	$123.35	$123.30
Purchase #6	$82.35	11.105%	$91.495	$91.50	$91.50	$91.50
Purchase #7	$35.30	12.624%	$39.7563	$39.76	$39.75	$39.80
7 purchase totals =	$964.88		$1,035.8699	$1,035.87	$1,035.80	$1,035.80