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	$65.30	11.817%	$73.0165	$73.02	$73.00	$73.00
Purchase #2	$43.69	11.172%	$48.571	$48.57	$48.55	$48.60
Purchase #3	$245.96	10.415%	$271.5767	$271.58	$271.60	$271.60
Purchase #4	$156.83	9.111%	$171.1188	$171.12	$171.10	$171.10
Purchase #5	$77.51	11.576%	$86.4826	$86.48	$86.50	$86.50
Purchase #6	$48.99	7.181%	$52.508	$52.51	$52.50	$52.50
Purchase #7	$124.37	5.810%	$131.5959	$131.60	$131.60	$131.60
7 purchase totals =	$762.65		$834.8695	$834.88	$834.85	$834.90