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	$129.34	7.670%	$139.2604	$139.26	$139.25	$139.30
Purchase #2	$10.39	8.387%	$11.2614	$11.26	$11.25	$11.30
Purchase #3	$103.49	7.401%	$111.1493	$111.15	$111.15	$111.10
Purchase #4	$61.59	10.632%	$68.1382	$68.14	$68.15	$68.10
Purchase #5	$198.82	6.566%	$211.8745	$211.87	$211.85	$211.90
Purchase #6	$169.76	11.252%	$188.8614	$188.86	$188.85	$188.90
Purchase #7	$231.28	6.527%	$246.3756	$246.38	$246.40	$246.40
7 purchase totals =	$904.67		$976.9208	$976.92	$976.90	$977.00