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	$84.70	5.748%	$89.5686	$89.57	$89.55	$89.60
Purchase #2	$175.71	3.228%	$181.3819	$181.38	$181.40	$181.40
Purchase #3	$35.72	5.417%	$37.655	$37.66	$37.65	$37.70
Purchase #4	$83.39	6.219%	$88.576	$88.58	$88.60	$88.60
Purchase #5	$81.45	4.788%	$85.3498	$85.35	$85.35	$85.30
Purchase #6	$73.46	3.518%	$76.0443	$76.04	$76.05	$76.00
Purchase #7	$122.44	3.163%	$126.3128	$126.31	$126.30	$126.30
7 purchase totals =	$656.87		$684.8884	$684.89	$684.90	$684.90