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	$187.34	7.236%	$200.8959	$200.90	$200.90	$200.90
Purchase #2	$245.69	4.429%	$256.5716	$256.57	$256.55	$256.60
Purchase #3	$204.75	9.161%	$223.5071	$223.51	$223.50	$223.50
Purchase #4	$53.25	12.809%	$60.0708	$60.07	$60.05	$60.10
Purchase #5	$81.32	6.234%	$86.3895	$86.39	$86.40	$86.40
Purchase #6	$39.25	13.171%	$44.4196	$44.42	$44.40	$44.40
Purchase #7	$137.54	6.465%	$146.432	$146.43	$146.45	$146.40
7 purchase totals =	$949.14		$1,018.2865	$1,018.29	$1,018.25	$1,018.30