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	$248.82	10.469%	$274.869	$274.87	$274.85	$274.90
Purchase #2	$123.60	6.280%	$131.3621	$131.36	$131.35	$131.40
Purchase #3	$20.97	13.445%	$23.7894	$23.79	$23.80	$23.80
Purchase #4	$122.91	11.428%	$136.9562	$136.96	$136.95	$137.00
Purchase #5	$12.76	6.480%	$13.5868	$13.59	$13.60	$13.60
Purchase #6	$42.39	6.356%	$45.0843	$45.08	$45.10	$45.10
Purchase #7	$94.89	5.667%	$100.2674	$100.27	$100.25	$100.30
7 purchase totals =	$666.34		$725.9152	$725.92	$725.90	$726.10