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	$11.54	9.660%	$12.6548	$12.65	$12.65	$12.70
Purchase #2	$39.41	10.118%	$43.3975	$43.40	$43.40	$43.40
Purchase #3	$71.39	13.864%	$81.2875	$81.29	$81.30	$81.30
Purchase #4	$70.34	11.732%	$78.5923	$78.59	$78.60	$78.60
Purchase #5	$39.85	9.157%	$43.4991	$43.50	$43.50	$43.50
Purchase #6	$37.74	12.808%	$42.5737	$42.57	$42.55	$42.60
Purchase #7	$96.48	13.231%	$109.2453	$109.25	$109.25	$109.20
7 purchase totals =	$366.75		$411.2502	$411.25	$411.25	$411.30