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	$109.72	9.114%	$119.7199	$119.72	$119.70	$119.70
Purchase #2	$109.50	7.408%	$117.6118	$117.61	$117.60	$117.60
Purchase #3	$62.76	11.848%	$70.1958	$70.20	$70.20	$70.20
Purchase #4	$147.87	3.788%	$153.4713	$153.47	$153.45	$153.50
Purchase #5	$203.34	4.222%	$211.925	$211.93	$211.95	$211.90
Purchase #6	$191.48	3.156%	$197.5231	$197.52	$197.50	$197.50
Purchase #7	$131.28	11.384%	$146.2249	$146.22	$146.20	$146.20
7 purchase totals =	$955.95		$1,016.6718	$1,016.67	$1,016.60	$1,016.60