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	$134.56	13.600%	$152.8602	$152.86	$152.85	$152.90
Purchase #2	$143.38	5.226%	$150.873	$150.87	$150.85	$150.90
Purchase #3	$183.48	9.155%	$200.2776	$200.28	$200.30	$200.30
Purchase #4	$83.92	8.834%	$91.3335	$91.33	$91.35	$91.30
Purchase #5	$88.37	10.320%	$97.4898	$97.49	$97.50	$97.50
Purchase #6	$41.50	5.211%	$43.6626	$43.66	$43.65	$43.70
Purchase #7	$9.64	9.103%	$10.5175	$10.52	$10.50	$10.50
7 purchase totals =	$684.85		$747.0142	$747.01	$747.00	$747.10