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	$196.57	11.576%	$219.3249	$219.32	$219.30	$219.30
Purchase #2	$61.89	11.184%	$68.8118	$68.81	$68.80	$68.80
Purchase #3	$39.95	4.797%	$41.8664	$41.87	$41.85	$41.90
Purchase #4	$144.27	5.792%	$152.6261	$152.63	$152.65	$152.60
Purchase #5	$238.44	5.632%	$251.8689	$251.87	$251.85	$251.90
Purchase #6	$141.76	9.752%	$155.5844	$155.58	$155.60	$155.60
Purchase #7	$85.42	4.718%	$89.4501	$89.45	$89.45	$89.50
7 purchase totals =	$908.30		$979.5326	$979.53	$979.50	$979.60