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	$136.44	10.314%	$150.5124	$150.51	$150.50	$150.50
Purchase #2	$99.95	11.697%	$111.6412	$111.64	$111.65	$111.60
Purchase #3	$22.99	5.830%	$24.3303	$24.33	$24.35	$24.30
Purchase #4	$16.80	9.871%	$18.4583	$18.46	$18.45	$18.50
Purchase #5	$97.28	8.721%	$105.7638	$105.76	$105.75	$105.80
Purchase #6	$110.46	8.430%	$119.7718	$119.77	$119.75	$119.80
Purchase #7	$227.30	11.669%	$253.8236	$253.82	$253.80	$253.80
7 purchase totals =	$711.22		$784.3014	$784.29	$784.25	$784.30