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	$246.34	8.192%	$266.5202	$266.52	$266.50	$266.50
Purchase #2	$28.94	10.442%	$31.9619	$31.96	$31.95	$32.00
Purchase #3	$69.96	11.343%	$77.8956	$77.90	$77.90	$77.90
Purchase #4	$219.97	9.357%	$240.5526	$240.55	$240.55	$240.60
Purchase #5	$48.62	8.213%	$52.6132	$52.61	$52.60	$52.60
Purchase #6	$60.35	12.445%	$67.8606	$67.86	$67.85	$67.90
Purchase #7	$196.84	13.735%	$223.876	$223.88	$223.90	$223.90
7 purchase totals =	$871.02		$961.2801	$961.28	$961.25	$961.40