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	$117.36	12.402%	$131.915	$131.92	$131.90	$131.90
Purchase #2	$7.91	11.342%	$8.8072	$8.81	$8.80	$8.80
Purchase #3	$100.95	4.666%	$105.6603	$105.66	$105.65	$105.70
Purchase #4	$40.30	8.268%	$43.632	$43.63	$43.65	$43.60
Purchase #5	$95.48	4.255%	$99.5427	$99.54	$99.55	$99.50
Purchase #6	$8.34	7.427%	$8.9594	$8.96	$8.95	$9.00
Purchase #7	$138.64	10.131%	$152.6856	$152.69	$152.70	$152.70
7 purchase totals =	$508.98		$551.2022	$551.21	$551.20	$551.20