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	$76.45	9.794%	$83.9375	$83.94	$83.95	$83.90
Purchase #2	$215.94	3.709%	$223.9492	$223.95	$223.95	$223.90
Purchase #3	$56.80	4.456%	$59.331	$59.33	$59.35	$59.30
Purchase #4	$145.73	10.193%	$160.5843	$160.58	$160.60	$160.60
Purchase #5	$32.70	11.592%	$36.4906	$36.49	$36.50	$36.50
Purchase #6	$88.85	11.588%	$99.1459	$99.15	$99.15	$99.10
Purchase #7	$15.40	6.809%	$16.4486	$16.45	$16.45	$16.40
7 purchase totals =	$631.87		$679.8871	$679.89	$679.95	$679.70