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	$125.85	6.187%	$133.6363	$133.64	$133.65	$133.60
Purchase #2	$9.78	11.660%	$10.9203	$10.92	$10.90	$10.90
Purchase #3	$76.83	11.264%	$85.4841	$85.48	$85.50	$85.50
Purchase #4	$45.65	7.846%	$49.2317	$49.23	$49.25	$49.20
Purchase #5	$137.30	11.322%	$152.8451	$152.85	$152.85	$152.80
Purchase #6	$150.98	3.323%	$155.9971	$156.00	$156.00	$156.00
Purchase #7	$157.80	13.675%	$179.3792	$179.38	$179.40	$179.40
7 purchase totals =	$704.19		$767.4938	$767.50	$767.55	$767.40