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	$103.42	10.167%	$113.9347	$113.93	$113.95	$113.90
Purchase #2	$99.47	4.763%	$104.2078	$104.21	$104.20	$104.20
Purchase #3	$91.39	8.645%	$99.2907	$99.29	$99.30	$99.30
Purchase #4	$133.65	10.625%	$147.8503	$147.85	$147.85	$147.90
Purchase #5	$181.86	5.298%	$191.4949	$191.49	$191.50	$191.50
Purchase #6	$51.33	13.171%	$58.0907	$58.09	$58.10	$58.10
Purchase #7	$216.83	12.145%	$243.164	$243.16	$243.15	$243.20
7 purchase totals =	$877.95		$958.0331	$958.02	$958.05	$958.10