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	$143.51	5.327%	$151.1548	$151.15	$151.15	$151.20
Purchase #2	$247.64	8.157%	$267.84	$267.84	$267.85	$267.80
Purchase #3	$170.79	6.502%	$181.8948	$181.89	$181.90	$181.90
Purchase #4	$225.30	9.140%	$245.8924	$245.89	$245.90	$245.90
Purchase #5	$27.55	8.364%	$29.8543	$29.85	$29.85	$29.90
Purchase #6	$140.58	11.177%	$156.2926	$156.29	$156.30	$156.30
Purchase #7	$51.34	5.106%	$53.9614	$53.96	$53.95	$54.00
7 purchase totals =	$1,006.71		$1,086.8903	$1,086.87	$1,086.90	$1,087.00