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	$100.84	13.697%	$114.6521	$114.65	$114.65	$114.70
Purchase #2	$139.53	7.160%	$149.5203	$149.52	$149.50	$149.50
Purchase #3	$25.59	11.265%	$28.4727	$28.47	$28.45	$28.50
Purchase #4	$11.52	7.605%	$12.3961	$12.40	$12.40	$12.40
Purchase #5	$102.84	11.331%	$114.4928	$114.49	$114.50	$114.50
Purchase #6	$195.79	10.799%	$216.9334	$216.93	$216.95	$216.90
Purchase #7	$64.78	10.406%	$71.521	$71.52	$71.50	$71.50
7 purchase totals =	$640.89		$707.9884	$707.98	$707.95	$708.00