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	$21.60	4.585%	$22.5904	$22.59	$22.60	$22.60
Purchase #2	$125.85	13.190%	$142.4496	$142.45	$142.45	$142.40
Purchase #3	$250.88	12.441%	$282.092	$282.09	$282.10	$282.10
Purchase #4	$218.85	11.684%	$244.4204	$244.42	$244.40	$244.40
Purchase #5	$95.99	6.331%	$102.0671	$102.07	$102.05	$102.10
Purchase #6	$67.74	6.385%	$72.0652	$72.07	$72.05	$72.10
Purchase #7	$250.89	9.750%	$275.3518	$275.35	$275.35	$275.40
7 purchase totals =	$1,031.80		$1,141.0365	$1,141.04	$1,141.00	$1,141.10