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	$235.63	11.871%	$263.6016	$263.60	$263.60	$263.60
Purchase #2	$42.30	3.449%	$43.7589	$43.76	$43.75	$43.80
Purchase #3	$147.36	10.423%	$162.7193	$162.72	$162.70	$162.70
Purchase #4	$56.26	10.489%	$62.1611	$62.16	$62.15	$62.20
Purchase #5	$42.89	11.255%	$47.7173	$47.72	$47.70	$47.70
Purchase #6	$20.33	5.216%	$21.3904	$21.39	$21.40	$21.40
Purchase #7	$63.59	5.210%	$66.903	$66.90	$66.90	$66.90
7 purchase totals =	$608.36		$668.2516	$668.25	$668.20	$668.30