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	$227.91	3.124%	$235.0299	$235.03	$235.05	$235.00
Purchase #2	$105.97	5.642%	$111.9488	$111.95	$111.95	$111.90
Purchase #3	$130.28	12.393%	$146.4256	$146.43	$146.45	$146.40
Purchase #4	$58.89	3.264%	$60.8122	$60.81	$60.80	$60.80
Purchase #5	$86.86	7.788%	$93.6247	$93.62	$93.60	$93.60
Purchase #6	$125.76	12.429%	$141.3907	$141.39	$141.40	$141.40
Purchase #7	$148.33	5.503%	$156.4926	$156.49	$156.50	$156.50
7 purchase totals =	$884.00		$945.7245	$945.72	$945.75	$945.60