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	$131.99	10.485%	$145.8292	$145.83	$145.85	$145.80
Purchase #2	$29.55	11.205%	$32.8611	$32.86	$32.85	$32.90
Purchase #3	$68.70	11.339%	$76.4899	$76.49	$76.50	$76.50
Purchase #4	$221.66	12.208%	$248.7203	$248.72	$248.70	$248.70
Purchase #5	$77.33	6.241%	$82.1562	$82.16	$82.15	$82.20
Purchase #6	$231.34	3.117%	$238.5509	$238.55	$238.55	$238.60
Purchase #7	$95.39	5.710%	$100.8368	$100.84	$100.85	$100.80
7 purchase totals =	$855.96		$925.4444	$925.45	$925.45	$925.50