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	$83.67	5.578%	$88.3371	$88.34	$88.35	$88.30
Purchase #2	$228.60	3.565%	$236.7496	$236.75	$236.75	$236.70
Purchase #3	$101.67	3.329%	$105.0546	$105.05	$105.05	$105.10
Purchase #4	$227.76	4.801%	$238.6948	$238.69	$238.70	$238.70
Purchase #5	$106.89	11.243%	$118.9076	$118.91	$118.90	$118.90
Purchase #6	$230.26	12.753%	$259.6251	$259.63	$259.65	$259.60
Purchase #7	$32.72	7.361%	$35.1285	$35.13	$35.15	$35.10
7 purchase totals =	$1,011.57		$1,082.4973	$1,082.50	$1,082.55	$1,082.40