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	$42.88	11.810%	$47.9441	$47.94	$47.95	$47.90
Purchase #2	$165.38	8.394%	$179.262	$179.26	$179.25	$179.30
Purchase #3	$78.49	10.558%	$86.777	$86.78	$86.80	$86.80
Purchase #4	$192.51	8.557%	$208.9831	$208.98	$209.00	$209.00
Purchase #5	$62.55	10.763%	$69.2823	$69.28	$69.30	$69.30
Purchase #6	$176.51	11.232%	$196.3356	$196.34	$196.35	$196.30
Purchase #7	$89.40	11.394%	$99.5862	$99.59	$99.60	$99.60
7 purchase totals =	$807.72		$888.1703	$888.17	$888.25	$888.20