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	$150.64	3.408%	$155.7738	$155.77	$155.75	$155.80
Purchase #2	$77.40	5.208%	$81.431	$81.43	$81.45	$81.40
Purchase #3	$136.32	5.733%	$144.1352	$144.14	$144.15	$144.10
Purchase #4	$102.77	3.196%	$106.0545	$106.05	$106.05	$106.10
Purchase #5	$7.86	5.207%	$8.2693	$8.27	$8.25	$8.30
Purchase #6	$233.70	12.223%	$262.2652	$262.27	$262.25	$262.30
Purchase #7	$238.35	6.790%	$254.534	$254.53	$254.55	$254.50
7 purchase totals =	$947.04		$1,012.4630	$1,012.46	$1,012.45	$1,012.50