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	$159.64	13.358%	$180.9647	$180.96	$180.95	$181.00
Purchase #2	$152.54	4.603%	$159.5614	$159.56	$159.55	$159.60
Purchase #3	$189.77	12.627%	$213.7323	$213.73	$213.75	$213.70
Purchase #4	$112.78	6.111%	$119.672	$119.67	$119.65	$119.70
Purchase #5	$100.87	9.504%	$110.4567	$110.46	$110.45	$110.50
Purchase #6	$34.33	9.192%	$37.4856	$37.49	$37.50	$37.50
Purchase #7	$180.59	7.506%	$194.1451	$194.15	$194.15	$194.10
7 purchase totals =	$930.52		$1,016.0178	$1,016.02	$1,016.00	$1,016.10