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	$68.29	7.264%	$73.2506	$73.25	$73.25	$73.30
Purchase #2	$85.65	7.541%	$92.1089	$92.11	$92.10	$92.10
Purchase #3	$132.79	12.535%	$149.4352	$149.44	$149.45	$149.40
Purchase #4	$80.92	7.426%	$86.9291	$86.93	$86.95	$86.90
Purchase #5	$126.69	10.330%	$139.7771	$139.78	$139.80	$139.80
Purchase #6	$75.92	10.144%	$83.6213	$83.62	$83.60	$83.60
Purchase #7	$34.59	9.511%	$37.8799	$37.88	$37.90	$37.90
7 purchase totals =	$604.85		$663.0021	$663.01	$663.05	$663.00