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	$243.54	11.629%	$271.8613	$271.86	$271.85	$271.90
Purchase #2	$124.90	4.313%	$130.2869	$130.29	$130.30	$130.30
Purchase #3	$103.81	8.597%	$112.7345	$112.73	$112.75	$112.70
Purchase #4	$118.48	6.567%	$126.2606	$126.26	$126.25	$126.30
Purchase #5	$225.29	9.356%	$246.3681	$246.37	$246.35	$246.40
Purchase #6	$71.48	10.269%	$78.8203	$78.82	$78.80	$78.80
Purchase #7	$243.69	11.522%	$271.768	$271.77	$271.75	$271.80
7 purchase totals =	$1,131.19		$1,238.0997	$1,238.10	$1,238.05	$1,238.20