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	$160.96	5.381%	$169.6213	$169.62	$169.60	$169.60
Purchase #2	$154.94	10.640%	$171.4256	$171.43	$171.45	$171.40
Purchase #3	$199.94	9.272%	$218.4784	$218.48	$218.50	$218.50
Purchase #4	$120.76	13.138%	$136.6254	$136.63	$136.65	$136.60
Purchase #5	$197.43	12.722%	$222.547	$222.55	$222.55	$222.50
Purchase #6	$230.74	11.202%	$256.5875	$256.59	$256.60	$256.60
Purchase #7	$32.54	7.504%	$34.9818	$34.98	$35.00	$35.00
7 purchase totals =	$1,097.31		$1,210.2670	$1,210.28	$1,210.35	$1,210.20