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	$86.68	4.727%	$90.7774	$90.78	$90.80	$90.80
Purchase #2	$72.63	4.517%	$75.9107	$75.91	$75.90	$75.90
Purchase #3	$186.83	3.296%	$192.9879	$192.99	$193.00	$193.00
Purchase #4	$95.90	10.834%	$106.2898	$106.29	$106.30	$106.30
Purchase #5	$186.76	5.175%	$196.4248	$196.42	$196.40	$196.40
Purchase #6	$100.65	9.203%	$109.9128	$109.91	$109.90	$109.90
Purchase #7	$11.82	11.582%	$13.189	$13.19	$13.20	$13.20
7 purchase totals =	$741.27		$785.4924	$785.49	$785.50	$785.50