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	$38.91	11.155%	$43.2504	$43.25	$43.25	$43.30
Purchase #2	$25.61	9.154%	$27.9543	$27.95	$27.95	$28.00
Purchase #3	$203.72	13.768%	$231.7682	$231.77	$231.75	$231.80
Purchase #4	$36.29	10.405%	$40.066	$40.07	$40.05	$40.10
Purchase #5	$72.59	7.820%	$78.2665	$78.27	$78.25	$78.30
Purchase #6	$55.69	13.778%	$63.363	$63.36	$63.35	$63.40
Purchase #7	$31.30	10.580%	$34.6115	$34.61	$34.60	$34.60
7 purchase totals =	$464.11		$519.2799	$519.28	$519.20	$519.50