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	$156.29	11.239%	$173.8554	$173.86	$173.85	$173.90
Purchase #2	$33.85	10.873%	$37.5305	$37.53	$37.55	$37.50
Purchase #3	$74.60	7.473%	$80.1749	$80.17	$80.15	$80.20
Purchase #4	$179.45	9.644%	$196.7562	$196.76	$196.75	$196.80
Purchase #5	$12.34	11.154%	$13.7164	$13.72	$13.70	$13.70
Purchase #6	$77.50	11.749%	$86.6055	$86.61	$86.60	$86.60
Purchase #7	$171.72	7.565%	$184.7106	$184.71	$184.70	$184.70
7 purchase totals =	$705.75		$773.3495	$773.36	$773.30	$773.40