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	$116.77	12.639%	$131.5286	$131.53	$131.55	$131.50
Purchase #2	$93.52	5.349%	$98.5224	$98.52	$98.50	$98.50
Purchase #3	$161.89	12.138%	$181.5402	$181.54	$181.55	$181.50
Purchase #4	$149.62	5.420%	$157.7294	$157.73	$157.75	$157.70
Purchase #5	$83.94	6.272%	$89.2047	$89.20	$89.20	$89.20
Purchase #6	$12.30	7.696%	$13.2466	$13.25	$13.25	$13.20
Purchase #7	$182.31	4.344%	$190.2295	$190.23	$190.25	$190.20
7 purchase totals =	$800.35		$862.0014	$862.00	$862.05	$861.80