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	$243.74	10.743%	$269.925	$269.93	$269.95	$269.90
Purchase #2	$150.86	7.802%	$162.6301	$162.63	$162.65	$162.60
Purchase #3	$208.94	6.476%	$222.471	$222.47	$222.45	$222.50
Purchase #4	$126.76	4.418%	$132.3603	$132.36	$132.35	$132.40
Purchase #5	$37.42	12.650%	$42.1536	$42.15	$42.15	$42.20
Purchase #6	$111.64	12.351%	$125.4287	$125.43	$125.45	$125.40
Purchase #7	$77.97	12.328%	$87.5821	$87.58	$87.60	$87.60
7 purchase totals =	$957.33		$1,042.5508	$1,042.55	$1,042.60	$1,042.60