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	$209.51	13.504%	$237.8022	$237.80	$237.80	$237.80
Purchase #2	$115.56	8.377%	$125.2405	$125.24	$125.25	$125.20
Purchase #3	$45.83	11.656%	$51.1719	$51.17	$51.15	$51.20
Purchase #4	$125.93	8.352%	$136.4477	$136.45	$136.45	$136.40
Purchase #5	$209.29	6.484%	$222.8604	$222.86	$222.85	$222.90
Purchase #6	$146.65	5.214%	$154.2963	$154.30	$154.30	$154.30
Purchase #7	$182.79	7.304%	$196.141	$196.14	$196.15	$196.10
7 purchase totals =	$1,035.56		$1,123.9600	$1,123.96	$1,123.95	$1,123.90