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	$110.66	13.803%	$125.9344	$125.93	$125.95	$125.90
Purchase #2	$141.36	6.624%	$150.7237	$150.72	$150.70	$150.70
Purchase #3	$59.69	5.566%	$63.0123	$63.01	$63.00	$63.00
Purchase #4	$226.33	12.215%	$253.9762	$253.98	$254.00	$254.00
Purchase #5	$83.58	7.220%	$89.6145	$89.61	$89.60	$89.60
Purchase #6	$108.51	10.324%	$119.7126	$119.71	$119.70	$119.70
Purchase #7	$128.89	10.654%	$142.6219	$142.62	$142.60	$142.60
7 purchase totals =	$859.02		$945.5956	$945.58	$945.55	$945.50