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	$83.25	7.611%	$89.5862	$89.59	$89.60	$89.60
Purchase #2	$37.37	8.439%	$40.5237	$40.52	$40.50	$40.50
Purchase #3	$5.94	13.138%	$6.7204	$6.72	$6.70	$6.70
Purchase #4	$189.66	3.473%	$196.2469	$196.25	$196.25	$196.20
Purchase #5	$69.70	10.431%	$76.9704	$76.97	$76.95	$77.00
Purchase #6	$181.69	13.171%	$205.6204	$205.62	$205.60	$205.60
Purchase #7	$156.27	8.433%	$169.4482	$169.45	$169.45	$169.40
7 purchase totals =	$723.88		$785.1162	$785.12	$785.05	$785.00