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	$206.37	8.209%	$223.3109	$223.31	$223.30	$223.30
Purchase #2	$160.35	4.306%	$167.2547	$167.25	$167.25	$167.30
Purchase #3	$122.55	7.564%	$131.8197	$131.82	$131.80	$131.80
Purchase #4	$151.73	8.563%	$164.7226	$164.72	$164.70	$164.70
Purchase #5	$77.95	10.433%	$86.0825	$86.08	$86.10	$86.10
Purchase #6	$153.62	9.112%	$167.6179	$167.62	$167.60	$167.60
Purchase #7	$130.47	10.320%	$143.9345	$143.93	$143.95	$143.90
7 purchase totals =	$1,003.04		$1,084.7428	$1,084.73	$1,084.70	$1,084.70