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	$219.27	13.865%	$249.6718	$249.67	$249.65	$249.70
Purchase #2	$32.54	6.252%	$34.5744	$34.57	$34.55	$34.60
Purchase #3	$40.41	7.619%	$43.4888	$43.49	$43.50	$43.50
Purchase #4	$99.47	3.556%	$103.0072	$103.01	$103.00	$103.00
Purchase #5	$71.90	13.642%	$81.7086	$81.71	$81.70	$81.70
Purchase #6	$21.72	10.764%	$24.0579	$24.06	$24.05	$24.10
Purchase #7	$137.97	9.317%	$150.8247	$150.82	$150.80	$150.80
7 purchase totals =	$623.28		$687.3334	$687.33	$687.25	$687.40