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	$138.38	3.619%	$143.388	$143.39	$143.40	$143.40
Purchase #2	$187.63	6.625%	$200.0605	$200.06	$200.05	$200.10
Purchase #3	$61.82	3.179%	$63.7853	$63.79	$63.80	$63.80
Purchase #4	$152.90	13.478%	$173.5079	$173.51	$173.50	$173.50
Purchase #5	$249.86	5.690%	$264.077	$264.08	$264.10	$264.10
Purchase #6	$221.67	5.854%	$234.6466	$234.65	$234.65	$234.60
Purchase #7	$78.82	8.212%	$85.2927	$85.29	$85.30	$85.30
7 purchase totals =	$1,091.08		$1,164.7580	$1,164.77	$1,164.80	$1,164.80