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	$53.25	4.562%	$55.6793	$55.68	$55.70	$55.70
Purchase #2	$150.36	11.692%	$167.9401	$167.94	$167.95	$167.90
Purchase #3	$73.70	10.433%	$81.3891	$81.39	$81.40	$81.40
Purchase #4	$245.26	10.123%	$270.0877	$270.09	$270.10	$270.10
Purchase #5	$93.53	12.304%	$105.0379	$105.04	$105.05	$105.00
Purchase #6	$143.29	5.799%	$151.5994	$151.60	$151.60	$151.60
Purchase #7	$157.37	4.630%	$164.6562	$164.66	$164.65	$164.70
7 purchase totals =	$916.76		$996.3897	$996.40	$996.45	$996.40