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	$140.25	9.333%	$153.3395	$153.34	$153.35	$153.30
Purchase #2	$204.78	8.501%	$222.1883	$222.19	$222.20	$222.20
Purchase #3	$237.58	5.662%	$251.0318	$251.03	$251.05	$251.00
Purchase #4	$213.39	3.807%	$221.5138	$221.51	$221.50	$221.50
Purchase #5	$101.33	10.441%	$111.9099	$111.91	$111.90	$111.90
Purchase #6	$142.49	12.215%	$159.8952	$159.90	$159.90	$159.90
Purchase #7	$53.94	12.414%	$60.6361	$60.64	$60.65	$60.60
7 purchase totals =	$1,093.76		$1,180.5146	$1,180.52	$1,180.55	$1,180.40