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	$82.94	7.601%	$89.2443	$89.24	$89.25	$89.20
Purchase #2	$131.90	7.395%	$141.654	$141.65	$141.65	$141.70
Purchase #3	$169.77	5.659%	$179.3773	$179.38	$179.40	$179.40
Purchase #4	$192.84	8.517%	$209.2642	$209.26	$209.25	$209.30
Purchase #5	$57.36	6.603%	$61.1475	$61.15	$61.15	$61.10
Purchase #6	$13.43	5.581%	$14.1795	$14.18	$14.20	$14.20
Purchase #7	$37.91	6.702%	$40.4507	$40.45	$40.45	$40.50
7 purchase totals =	$686.15		$735.3175	$735.31	$735.35	$735.40