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	$147.34	10.173%	$162.3289	$162.33	$162.35	$162.30
Purchase #2	$40.48	9.111%	$44.1681	$44.17	$44.15	$44.20
Purchase #3	$76.53	9.165%	$83.544	$83.54	$83.55	$83.50
Purchase #4	$215.39	3.193%	$222.2674	$222.27	$222.25	$222.30
Purchase #5	$136.99	12.253%	$153.7754	$153.78	$153.80	$153.80
Purchase #6	$148.82	13.430%	$168.8065	$168.81	$168.80	$168.80
Purchase #7	$29.59	11.322%	$32.9402	$32.94	$32.95	$32.90
7 purchase totals =	$795.14		$867.8305	$867.84	$867.85	$867.80