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	$169.77	12.750%	$191.4157	$191.42	$191.40	$191.40
Purchase #2	$181.26	4.512%	$189.4385	$189.44	$189.45	$189.40
Purchase #3	$30.55	3.816%	$31.7158	$31.72	$31.70	$31.70
Purchase #4	$245.29	4.147%	$255.4622	$255.46	$255.45	$255.50
Purchase #5	$190.95	4.655%	$199.8387	$199.84	$199.85	$199.80
Purchase #6	$176.60	8.465%	$191.5492	$191.55	$191.55	$191.50
Purchase #7	$75.68	12.550%	$85.1778	$85.18	$85.20	$85.20
7 purchase totals =	$1,070.10		$1,144.5979	$1,144.61	$1,144.60	$1,144.50