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	$172.33	7.558%	$185.3547	$185.35	$185.35	$185.40
Purchase #2	$205.95	4.400%	$215.0118	$215.01	$215.00	$215.00
Purchase #3	$193.31	11.753%	$216.0297	$216.03	$216.05	$216.00
Purchase #4	$138.47	13.222%	$156.7785	$156.78	$156.80	$156.80
Purchase #5	$212.28	4.126%	$221.0387	$221.04	$221.05	$221.00
Purchase #6	$66.56	6.232%	$70.708	$70.71	$70.70	$70.70
Purchase #7	$84.86	5.655%	$89.6588	$89.66	$89.65	$89.70
7 purchase totals =	$1,073.76		$1,154.5802	$1,154.58	$1,154.60	$1,154.60