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	$161.40	13.179%	$182.6709	$182.67	$182.65	$182.70
Purchase #2	$206.78	7.860%	$223.0329	$223.03	$223.05	$223.00
Purchase #3	$82.77	7.512%	$88.9877	$88.99	$89.00	$89.00
Purchase #4	$167.61	7.618%	$180.3785	$180.38	$180.40	$180.40
Purchase #5	$42.59	7.863%	$45.9389	$45.94	$45.95	$45.90
Purchase #6	$133.66	11.594%	$149.1565	$149.16	$149.15	$149.20
Purchase #7	$32.88	4.677%	$34.4178	$34.42	$34.40	$34.40
7 purchase totals =	$827.69		$904.5832	$904.59	$904.60	$904.60