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	$222.95	3.722%	$231.2482	$231.25	$231.25	$231.20
Purchase #2	$30.83	3.510%	$31.9121	$31.91	$31.90	$31.90
Purchase #3	$79.52	4.819%	$83.3521	$83.35	$83.35	$83.40
Purchase #4	$249.62	3.460%	$258.2569	$258.26	$258.25	$258.30
Purchase #5	$144.37	5.460%	$152.2526	$152.25	$152.25	$152.30
Purchase #6	$199.47	11.466%	$222.3412	$222.34	$222.35	$222.30
Purchase #7	$146.96	9.292%	$160.6155	$160.62	$160.60	$160.60
7 purchase totals =	$1,073.72		$1,139.9786	$1,139.98	$1,139.95	$1,140.00