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	$123.44	8.118%	$133.4609	$133.46	$133.45	$133.50
Purchase #2	$230.85	5.485%	$243.5121	$243.51	$243.50	$243.50
Purchase #3	$165.78	3.482%	$171.5525	$171.55	$171.55	$171.60
Purchase #4	$108.34	4.145%	$112.8307	$112.83	$112.85	$112.80
Purchase #5	$226.34	8.564%	$245.7238	$245.72	$245.70	$245.70
Purchase #6	$116.53	8.581%	$126.5294	$126.53	$126.55	$126.50
Purchase #7	$137.51	9.296%	$150.2929	$150.29	$150.30	$150.30
7 purchase totals =	$1,108.79		$1,183.9023	$1,183.89	$1,183.90	$1,183.90