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	$139.39	6.565%	$148.541	$148.54	$148.55	$148.50
Purchase #2	$30.32	10.424%	$33.4806	$33.48	$33.50	$33.50
Purchase #3	$21.73	3.797%	$22.5551	$22.56	$22.55	$22.60
Purchase #4	$18.89	10.445%	$20.8631	$20.86	$20.85	$20.90
Purchase #5	$228.96	13.118%	$258.995	$259.00	$259.00	$259.00
Purchase #6	$42.52	7.716%	$45.8008	$45.80	$45.80	$45.80
Purchase #7	$147.59	4.820%	$154.7038	$154.70	$154.70	$154.70
7 purchase totals =	$629.40		$684.9394	$684.94	$684.95	$685.00