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	$164.54	3.308%	$169.983	$169.98	$170.00	$170.00
Purchase #2	$224.43	10.208%	$247.3398	$247.34	$247.35	$247.30
Purchase #3	$141.94	6.609%	$151.3208	$151.32	$151.30	$151.30
Purchase #4	$20.33	6.192%	$21.5888	$21.59	$21.60	$21.60
Purchase #5	$185.26	6.240%	$196.8202	$196.82	$196.80	$196.80
Purchase #6	$217.43	9.610%	$238.325	$238.33	$238.35	$238.30
Purchase #7	$186.83	10.247%	$205.9745	$205.97	$205.95	$206.00
7 purchase totals =	$1,140.76		$1,231.3521	$1,231.35	$1,231.35	$1,231.30