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	$135.47	11.828%	$151.4934	$151.49	$151.50	$151.50
Purchase #2	$173.36	10.376%	$191.3478	$191.35	$191.35	$191.30
Purchase #3	$67.34	5.541%	$71.0713	$71.07	$71.05	$71.10
Purchase #4	$106.48	7.630%	$114.6044	$114.60	$114.60	$114.60
Purchase #5	$231.40	11.198%	$257.3122	$257.31	$257.30	$257.30
Purchase #6	$150.89	9.729%	$165.5701	$165.57	$165.55	$165.60
Purchase #7	$165.53	6.648%	$176.5344	$176.53	$176.55	$176.50
7 purchase totals =	$1,030.47		$1,127.9336	$1,127.92	$1,127.90	$1,127.90