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	$199.28	11.162%	$221.5236	$221.52	$221.50	$221.50
Purchase #2	$86.53	9.456%	$94.7123	$94.71	$94.70	$94.70
Purchase #3	$60.28	11.173%	$67.0151	$67.02	$67.00	$67.00
Purchase #4	$126.46	13.306%	$143.2868	$143.29	$143.30	$143.30
Purchase #5	$145.72	4.547%	$152.3459	$152.35	$152.35	$152.30
Purchase #6	$128.41	12.224%	$144.1068	$144.11	$144.10	$144.10
Purchase #7	$202.89	11.862%	$226.9568	$226.96	$226.95	$227.00
7 purchase totals =	$949.57		$1,049.9473	$1,049.96	$1,049.90	$1,049.90