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	$34.32	4.376%	$35.8218	$35.82	$35.80	$35.80
Purchase #2	$155.88	3.660%	$161.5852	$161.59	$161.60	$161.60
Purchase #3	$160.35	4.175%	$167.0446	$167.04	$167.05	$167.00
Purchase #4	$152.74	7.841%	$164.7163	$164.72	$164.70	$164.70
Purchase #5	$221.34	6.377%	$235.4549	$235.45	$235.45	$235.50
Purchase #6	$247.88	5.533%	$261.5952	$261.60	$261.60	$261.60
Purchase #7	$78.96	13.463%	$89.5904	$89.59	$89.60	$89.60
7 purchase totals =	$1,051.47		$1,115.8084	$1,115.81	$1,115.80	$1,115.80