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	$122.82	13.788%	$139.7544	$139.75	$139.75	$139.80
Purchase #2	$224.32	13.596%	$254.8185	$254.82	$254.80	$254.80
Purchase #3	$145.64	13.635%	$165.498	$165.50	$165.50	$165.50
Purchase #4	$40.79	13.201%	$46.1747	$46.17	$46.15	$46.20
Purchase #5	$56.64	12.633%	$63.7953	$63.80	$63.80	$63.80
Purchase #6	$109.74	12.788%	$123.7736	$123.77	$123.75	$123.80
Purchase #7	$244.78	8.491%	$265.5643	$265.56	$265.55	$265.60
7 purchase totals =	$944.73		$1,059.3788	$1,059.37	$1,059.30	$1,059.50