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	$57.90	10.337%	$63.8851	$63.89	$63.90	$63.90
Purchase #2	$172.36	4.591%	$180.273	$180.27	$180.25	$180.30
Purchase #3	$98.65	6.539%	$105.1007	$105.10	$105.10	$105.10
Purchase #4	$173.65	6.226%	$184.4614	$184.46	$184.45	$184.50
Purchase #5	$227.39	13.837%	$258.854	$258.85	$258.85	$258.90
Purchase #6	$136.88	11.653%	$152.8306	$152.83	$152.85	$152.80
Purchase #7	$93.95	3.491%	$97.2298	$97.23	$97.25	$97.20
7 purchase totals =	$960.78		$1,042.6346	$1,042.63	$1,042.65	$1,042.70