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	$209.93	5.843%	$222.1962	$222.20	$222.20	$222.20
Purchase #2	$74.44	5.483%	$78.5215	$78.52	$78.50	$78.50
Purchase #3	$208.80	6.555%	$222.4868	$222.49	$222.50	$222.50
Purchase #4	$54.46	12.617%	$61.3312	$61.33	$61.35	$61.30
Purchase #5	$225.33	8.250%	$243.9197	$243.92	$243.90	$243.90
Purchase #6	$208.76	9.106%	$227.7697	$227.77	$227.75	$227.80
Purchase #7	$93.83	11.710%	$104.8175	$104.82	$104.80	$104.80
7 purchase totals =	$1,075.55		$1,161.0426	$1,161.05	$1,161.00	$1,161.00