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	$152.55	10.645%	$168.7889	$168.79	$168.80	$168.80
Purchase #2	$27.61	9.429%	$30.2133	$30.21	$30.20	$30.20
Purchase #3	$5.89	10.699%	$6.5202	$6.52	$6.50	$6.50
Purchase #4	$89.39	3.447%	$92.4713	$92.47	$92.45	$92.50
Purchase #5	$235.73	4.256%	$245.7627	$245.76	$245.75	$245.80
Purchase #6	$113.82	8.338%	$123.3103	$123.31	$123.30	$123.30
Purchase #7	$246.25	6.233%	$261.5988	$261.60	$261.60	$261.60
7 purchase totals =	$871.24		$928.6655	$928.66	$928.60	$928.70