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	$117.42	4.630%	$122.8565	$122.86	$122.85	$122.90
Purchase #2	$66.89	7.167%	$71.684	$71.68	$71.70	$71.70
Purchase #3	$160.65	11.469%	$179.0749	$179.07	$179.05	$179.10
Purchase #4	$109.61	3.395%	$113.3313	$113.33	$113.35	$113.30
Purchase #5	$162.79	9.854%	$178.8313	$178.83	$178.85	$178.80
Purchase #6	$170.83	7.717%	$184.013	$184.01	$184.00	$184.00
Purchase #7	$79.72	12.451%	$89.6459	$89.65	$89.65	$89.60
7 purchase totals =	$867.91		$939.4369	$939.43	$939.45	$939.40