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	$187.72	11.294%	$208.9211	$208.92	$208.90	$208.90
Purchase #2	$219.68	10.310%	$242.329	$242.33	$242.35	$242.30
Purchase #3	$123.34	10.266%	$136.0021	$136.00	$136.00	$136.00
Purchase #4	$74.59	5.193%	$78.4635	$78.46	$78.45	$78.50
Purchase #5	$92.58	12.687%	$104.3256	$104.33	$104.35	$104.30
Purchase #6	$176.65	3.480%	$182.7974	$182.80	$182.80	$182.80
Purchase #7	$92.74	3.806%	$96.2697	$96.27	$96.25	$96.30
7 purchase totals =	$967.30		$1,049.1084	$1,049.11	$1,049.10	$1,049.10