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	$185.70	5.713%	$196.309	$196.31	$196.30	$196.30
Purchase #2	$171.66	4.193%	$178.8577	$178.86	$178.85	$178.90
Purchase #3	$63.54	12.671%	$71.5912	$71.59	$71.60	$71.60
Purchase #4	$150.34	4.624%	$157.2917	$157.29	$157.30	$157.30
Purchase #5	$30.58	7.484%	$32.8686	$32.87	$32.85	$32.90
Purchase #6	$222.81	10.193%	$245.521	$245.52	$245.50	$245.50
Purchase #7	$239.40	12.140%	$268.4632	$268.46	$268.45	$268.50
7 purchase totals =	$1,064.03		$1,150.9024	$1,150.90	$1,150.85	$1,151.00