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	$99.29	9.800%	$109.0204	$109.02	$109.00	$109.00
Purchase #2	$221.52	9.557%	$242.6907	$242.69	$242.70	$242.70
Purchase #3	$210.91	8.137%	$228.0717	$228.07	$228.05	$228.10
Purchase #4	$122.31	7.698%	$131.7254	$131.73	$131.75	$131.70
Purchase #5	$10.87	11.363%	$12.1052	$12.11	$12.10	$12.10
Purchase #6	$215.93	8.714%	$234.7461	$234.75	$234.75	$234.70
Purchase #7	$224.34	6.308%	$238.4914	$238.49	$238.50	$238.50
7 purchase totals =	$1,105.17		$1,196.8509	$1,196.86	$1,196.85	$1,196.80