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	$226.78	7.161%	$243.0197	$243.02	$243.00	$243.00
Purchase #2	$88.39	13.549%	$100.366	$100.37	$100.35	$100.40
Purchase #3	$39.84	8.650%	$43.2862	$43.29	$43.30	$43.30
Purchase #4	$55.85	8.236%	$60.4498	$60.45	$60.45	$60.40
Purchase #5	$110.82	7.840%	$119.5083	$119.51	$119.50	$119.50
Purchase #6	$82.62	8.847%	$89.9294	$89.93	$89.95	$89.90
Purchase #7	$219.65	10.542%	$242.8055	$242.81	$242.80	$242.80
7 purchase totals =	$823.95		$899.3649	$899.38	$899.35	$899.30