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	$142.26	5.733%	$150.4158	$150.42	$150.40	$150.40
Purchase #2	$250.94	3.861%	$260.6288	$260.63	$260.65	$260.60
Purchase #3	$31.54	6.501%	$33.5904	$33.59	$33.60	$33.60
Purchase #4	$106.68	8.741%	$116.0049	$116.00	$116.00	$116.00
Purchase #5	$50.56	8.552%	$54.8839	$54.88	$54.90	$54.90
Purchase #6	$190.38	10.367%	$210.1167	$210.12	$210.10	$210.10
Purchase #7	$212.93	4.226%	$221.9284	$221.93	$221.95	$221.90
7 purchase totals =	$985.29		$1,047.5689	$1,047.57	$1,047.60	$1,047.50