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	$50.33	6.265%	$53.4832	$53.48	$53.50	$53.50
Purchase #2	$123.34	11.840%	$137.9435	$137.94	$137.95	$137.90
Purchase #3	$9.86	5.566%	$10.4088	$10.41	$10.40	$10.40
Purchase #4	$137.28	6.149%	$145.7213	$145.72	$145.70	$145.70
Purchase #5	$100.46	11.250%	$111.7618	$111.76	$111.75	$111.80
Purchase #6	$190.48	3.280%	$196.7277	$196.73	$196.75	$196.70
Purchase #7	$84.61	12.626%	$95.2929	$95.29	$95.30	$95.30
7 purchase totals =	$696.36		$751.3392	$751.33	$751.35	$751.30