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	$55.40	4.421%	$57.8492	$57.85	$57.85	$57.80
Purchase #2	$209.86	10.133%	$231.1251	$231.13	$231.15	$231.10
Purchase #3	$123.79	10.250%	$136.4785	$136.48	$136.50	$136.50
Purchase #4	$227.47	11.671%	$254.018	$254.02	$254.00	$254.00
Purchase #5	$19.96	7.196%	$21.3963	$21.40	$21.40	$21.40
Purchase #6	$178.48	4.510%	$186.5294	$186.53	$186.55	$186.50
Purchase #7	$53.75	13.505%	$61.0089	$61.01	$61.00	$61.00
7 purchase totals =	$868.71		$948.4054	$948.42	$948.45	$948.30