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	$84.39	3.421%	$87.277	$87.28	$87.30	$87.30
Purchase #2	$67.82	7.460%	$72.8794	$72.88	$72.90	$72.90
Purchase #3	$55.82	4.763%	$58.4787	$58.48	$58.50	$58.50
Purchase #4	$195.71	13.821%	$222.7591	$222.76	$222.75	$222.80
Purchase #5	$108.42	4.817%	$113.6426	$113.64	$113.65	$113.60
Purchase #6	$230.76	4.301%	$240.685	$240.69	$240.70	$240.70
Purchase #7	$224.56	7.642%	$241.7209	$241.72	$241.70	$241.70
7 purchase totals =	$967.48		$1,037.4427	$1,037.45	$1,037.50	$1,037.50