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	$162.91	6.624%	$173.7012	$173.70	$173.70	$173.70
Purchase #2	$71.86	13.787%	$81.7673	$81.77	$81.75	$81.80
Purchase #3	$200.82	5.808%	$212.4836	$212.48	$212.50	$212.50
Purchase #4	$52.41	13.239%	$59.3486	$59.35	$59.35	$59.30
Purchase #5	$198.65	9.439%	$217.4006	$217.40	$217.40	$217.40
Purchase #6	$165.84	11.720%	$185.2764	$185.28	$185.30	$185.30
Purchase #7	$65.26	13.128%	$73.8273	$73.83	$73.85	$73.80
7 purchase totals =	$917.75		$1,003.8050	$1,003.81	$1,003.85	$1,003.80