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	$85.99	5.485%	$90.7066	$90.71	$90.70	$90.70
Purchase #2	$89.53	11.198%	$99.5556	$99.56	$99.55	$99.60
Purchase #3	$54.90	11.738%	$61.3442	$61.34	$61.35	$61.30
Purchase #4	$193.31	13.236%	$218.8965	$218.90	$218.90	$218.90
Purchase #5	$248.65	6.756%	$265.4488	$265.45	$265.45	$265.40
Purchase #6	$88.56	6.648%	$94.4475	$94.45	$94.45	$94.40
Purchase #7	$107.87	4.262%	$112.4674	$112.47	$112.45	$112.50
7 purchase totals =	$868.81		$942.8666	$942.88	$942.85	$942.80