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	$165.75	9.761%	$181.9289	$181.93	$181.95	$181.90
Purchase #2	$133.31	11.599%	$148.7726	$148.77	$148.75	$148.80
Purchase #3	$84.26	11.807%	$94.2086	$94.21	$94.20	$94.20
Purchase #4	$75.48	4.487%	$78.8668	$78.87	$78.85	$78.90
Purchase #5	$112.60	10.152%	$124.0312	$124.03	$124.05	$124.00
Purchase #6	$145.32	13.843%	$165.4366	$165.44	$165.45	$165.40
Purchase #7	$40.33	8.118%	$43.604	$43.60	$43.60	$43.60
7 purchase totals =	$757.05		$836.8487	$836.85	$836.85	$836.80