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	$135.91	12.815%	$153.3269	$153.33	$153.35	$153.30
Purchase #2	$194.55	11.794%	$217.4952	$217.50	$217.50	$217.50
Purchase #3	$51.52	13.593%	$58.5231	$58.52	$58.50	$58.50
Purchase #4	$167.62	11.776%	$187.3589	$187.36	$187.35	$187.40
Purchase #5	$144.81	8.576%	$157.2289	$157.23	$157.25	$157.20
Purchase #6	$85.60	6.236%	$90.938	$90.94	$90.95	$90.90
Purchase #7	$247.89	12.470%	$278.8019	$278.80	$278.80	$278.80
7 purchase totals =	$1,027.90		$1,143.6729	$1,143.68	$1,143.70	$1,143.60