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	$181.73	8.141%	$196.5246	$196.52	$196.50	$196.50
Purchase #2	$144.69	6.546%	$154.1614	$154.16	$154.15	$154.20
Purchase #3	$59.66	12.865%	$67.3353	$67.34	$67.35	$67.30
Purchase #4	$146.60	3.740%	$152.0828	$152.08	$152.10	$152.10
Purchase #5	$12.91	8.354%	$13.9885	$13.99	$14.00	$14.00
Purchase #6	$112.49	12.317%	$126.3454	$126.35	$126.35	$126.30
Purchase #7	$126.25	4.661%	$132.1345	$132.13	$132.15	$132.10
7 purchase totals =	$784.33		$842.5725	$842.57	$842.60	$842.50