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	$60.50	7.113%	$64.8034	$64.80	$64.80	$64.80
Purchase #2	$168.75	3.761%	$175.0967	$175.10	$175.10	$175.10
Purchase #3	$42.81	5.130%	$45.0062	$45.01	$45.00	$45.00
Purchase #4	$36.54	10.630%	$40.4242	$40.42	$40.40	$40.40
Purchase #5	$169.59	9.119%	$185.0549	$185.05	$185.05	$185.10
Purchase #6	$86.88	4.684%	$90.9495	$90.95	$90.95	$90.90
Purchase #7	$31.54	13.401%	$35.7667	$35.77	$35.75	$35.80
7 purchase totals =	$596.61		$637.1016	$637.10	$637.05	$637.10