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	$173.47	13.473%	$196.8416	$196.84	$196.85	$196.80
Purchase #2	$87.46	4.861%	$91.7114	$91.71	$91.70	$91.70
Purchase #3	$134.69	9.489%	$147.4707	$147.47	$147.45	$147.50
Purchase #4	$98.58	4.341%	$102.8594	$102.86	$102.85	$102.90
Purchase #5	$157.51	13.393%	$178.6053	$178.61	$178.60	$178.60
Purchase #6	$225.57	6.319%	$239.8238	$239.82	$239.80	$239.80
Purchase #7	$140.71	5.557%	$148.5293	$148.53	$148.55	$148.50
7 purchase totals =	$1,017.99		$1,105.8415	$1,105.84	$1,105.80	$1,105.80