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	$38.49	12.532%	$43.3136	$43.31	$43.30	$43.30
Purchase #2	$195.60	10.138%	$215.4299	$215.43	$215.45	$215.40
Purchase #3	$162.48	5.252%	$171.0134	$171.01	$171.00	$171.00
Purchase #4	$137.61	8.148%	$148.8225	$148.82	$148.80	$148.80
Purchase #5	$32.38	4.146%	$33.7225	$33.72	$33.70	$33.70
Purchase #6	$164.46	3.210%	$169.7392	$169.74	$169.75	$169.70
Purchase #7	$73.58	6.818%	$78.5967	$78.60	$78.60	$78.60
7 purchase totals =	$804.60		$860.6378	$860.63	$860.60	$860.50