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	$68.71	3.540%	$71.1423	$71.14	$71.15	$71.10
Purchase #2	$246.47	11.588%	$275.0309	$275.03	$275.05	$275.00
Purchase #3	$105.59	8.318%	$114.373	$114.37	$114.35	$114.40
Purchase #4	$106.87	4.575%	$111.7593	$111.76	$111.75	$111.80
Purchase #5	$34.35	4.252%	$35.8106	$35.81	$35.80	$35.80
Purchase #6	$121.90	4.139%	$126.9454	$126.95	$126.95	$126.90
Purchase #7	$107.56	6.694%	$114.7601	$114.76	$114.75	$114.80
7 purchase totals =	$791.45		$849.8216	$849.82	$849.80	$849.80