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	$187.60	13.473%	$212.8753	$212.88	$212.90	$212.90
Purchase #2	$234.25	4.754%	$245.3862	$245.39	$245.40	$245.40
Purchase #3	$191.26	10.358%	$211.0707	$211.07	$211.05	$211.10
Purchase #4	$69.90	12.367%	$78.5445	$78.54	$78.55	$78.50
Purchase #5	$52.90	12.488%	$59.5062	$59.51	$59.50	$59.50
Purchase #6	$120.83	4.457%	$126.2154	$126.22	$126.20	$126.20
Purchase #7	$212.92	8.832%	$231.7251	$231.73	$231.75	$231.70
7 purchase totals =	$1,069.66		$1,165.3234	$1,165.34	$1,165.35	$1,165.30