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	$212.25	7.645%	$228.4765	$228.48	$228.50	$228.50
Purchase #2	$209.50	6.789%	$223.723	$223.72	$223.70	$223.70
Purchase #3	$195.45	7.710%	$210.5192	$210.52	$210.50	$210.50
Purchase #4	$99.40	6.144%	$105.5071	$105.51	$105.50	$105.50
Purchase #5	$26.89	10.843%	$29.8057	$29.81	$29.80	$29.80
Purchase #6	$14.40	4.335%	$15.0242	$15.02	$15.00	$15.00
Purchase #7	$181.47	4.826%	$190.2277	$190.23	$190.25	$190.20
7 purchase totals =	$939.36		$1,003.2834	$1,003.29	$1,003.25	$1,003.20