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	$30.46	7.443%	$32.7271	$32.73	$32.75	$32.70
Purchase #2	$244.46	4.841%	$256.2943	$256.29	$256.30	$256.30
Purchase #3	$23.27	11.376%	$25.9172	$25.92	$25.90	$25.90
Purchase #4	$18.65	4.404%	$19.4713	$19.47	$19.45	$19.50
Purchase #5	$209.61	7.501%	$225.3328	$225.33	$225.35	$225.30
Purchase #6	$235.45	10.556%	$260.3041	$260.30	$260.30	$260.30
Purchase #7	$192.84	3.481%	$199.5528	$199.55	$199.55	$199.60
7 purchase totals =	$954.74		$1,019.5996	$1,019.59	$1,019.60	$1,019.60