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	$147.40	11.283%	$164.0311	$164.03	$164.05	$164.00
Purchase #2	$18.39	12.363%	$20.6636	$20.66	$20.65	$20.70
Purchase #3	$116.94	7.338%	$125.5211	$125.52	$125.50	$125.50
Purchase #4	$178.42	12.413%	$200.5673	$200.57	$200.55	$200.60
Purchase #5	$18.36	5.398%	$19.3511	$19.35	$19.35	$19.40
Purchase #6	$92.38	7.291%	$99.1154	$99.12	$99.10	$99.10
Purchase #7	$228.65	10.851%	$253.4608	$253.46	$253.45	$253.50
7 purchase totals =	$800.54		$882.7104	$882.71	$882.65	$882.80