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	$164.41	12.730%	$185.3394	$185.34	$185.35	$185.30
Purchase #2	$54.79	6.431%	$58.3135	$58.31	$58.30	$58.30
Purchase #3	$145.67	6.700%	$155.4299	$155.43	$155.45	$155.40
Purchase #4	$208.83	10.634%	$231.037	$231.04	$231.05	$231.00
Purchase #5	$221.28	10.621%	$244.7821	$244.78	$244.80	$244.80
Purchase #6	$219.27	4.207%	$228.4947	$228.49	$228.50	$228.50
Purchase #7	$36.79	12.462%	$41.3748	$41.37	$41.35	$41.40
7 purchase totals =	$1,051.04		$1,144.7714	$1,144.76	$1,144.80	$1,144.70