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	$6.87	10.222%	$7.5723	$7.57	$7.55	$7.60
Purchase #2	$111.98	8.849%	$121.8891	$121.89	$121.90	$121.90
Purchase #3	$167.77	9.460%	$183.641	$183.64	$183.65	$183.60
Purchase #4	$175.93	11.471%	$196.1109	$196.11	$196.10	$196.10
Purchase #5	$110.36	7.564%	$118.7076	$118.71	$118.70	$118.70
Purchase #6	$95.70	11.207%	$106.4251	$106.43	$106.45	$106.40
Purchase #7	$30.54	7.724%	$32.8989	$32.90	$32.90	$32.90
7 purchase totals =	$699.15		$767.2449	$767.25	$767.25	$767.20