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	$177.44	4.353%	$185.164	$185.16	$185.15	$185.20
Purchase #2	$73.38	6.307%	$78.0081	$78.01	$78.00	$78.00
Purchase #3	$216.48	13.536%	$245.7827	$245.78	$245.80	$245.80
Purchase #4	$116.72	9.123%	$127.3684	$127.37	$127.35	$127.40
Purchase #5	$185.31	5.856%	$196.1618	$196.16	$196.15	$196.20
Purchase #6	$207.41	4.588%	$216.926	$216.93	$216.95	$216.90
Purchase #7	$157.74	7.253%	$169.1809	$169.18	$169.20	$169.20
7 purchase totals =	$1,134.48		$1,218.5919	$1,218.59	$1,218.60	$1,218.70