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	$70.86	11.443%	$78.9685	$78.97	$78.95	$79.00
Purchase #2	$6.53	10.566%	$7.22	$7.22	$7.20	$7.20
Purchase #3	$172.29	9.343%	$188.3871	$188.39	$188.40	$188.40
Purchase #4	$218.47	4.548%	$228.406	$228.41	$228.40	$228.40
Purchase #5	$37.68	12.662%	$42.451	$42.45	$42.45	$42.50
Purchase #6	$60.32	10.139%	$66.4358	$66.44	$66.45	$66.40
Purchase #7	$150.41	4.549%	$157.2522	$157.25	$157.25	$157.30
7 purchase totals =	$716.56		$769.1206	$769.13	$769.10	$769.20