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	$101.64	10.819%	$112.6364	$112.64	$112.65	$112.60
Purchase #2	$36.44	8.341%	$39.4795	$39.48	$39.50	$39.50
Purchase #3	$32.78	3.375%	$33.8863	$33.89	$33.90	$33.90
Purchase #4	$165.85	5.490%	$174.9552	$174.96	$174.95	$175.00
Purchase #5	$18.94	11.300%	$21.0802	$21.08	$21.10	$21.10
Purchase #6	$37.80	9.253%	$41.2976	$41.30	$41.30	$41.30
Purchase #7	$176.90	3.526%	$183.1375	$183.14	$183.15	$183.10
7 purchase totals =	$570.35		$606.4727	$606.49	$606.55	$606.50