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	$150.45	3.245%	$155.3321	$155.33	$155.35	$155.30
Purchase #2	$106.78	11.786%	$119.3651	$119.37	$119.35	$119.40
Purchase #3	$39.94	12.756%	$45.0347	$45.03	$45.05	$45.00
Purchase #4	$110.82	11.312%	$123.356	$123.36	$123.35	$123.40
Purchase #5	$37.50	5.264%	$39.474	$39.47	$39.45	$39.50
Purchase #6	$52.80	10.472%	$58.3292	$58.33	$58.35	$58.30
Purchase #7	$216.92	13.125%	$245.3908	$245.39	$245.40	$245.40
7 purchase totals =	$715.21		$786.2819	$786.28	$786.30	$786.30