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	$71.71	6.864%	$76.6322	$76.63	$76.65	$76.60
Purchase #2	$228.83	13.807%	$260.4246	$260.42	$260.40	$260.40
Purchase #3	$188.49	3.238%	$194.5933	$194.59	$194.60	$194.60
Purchase #4	$51.72	8.359%	$56.0433	$56.04	$56.05	$56.00
Purchase #5	$156.39	3.658%	$162.1107	$162.11	$162.10	$162.10
Purchase #6	$40.37	10.510%	$44.6129	$44.61	$44.60	$44.60
Purchase #7	$112.87	12.541%	$127.025	$127.03	$127.05	$127.00
7 purchase totals =	$850.38		$921.4420	$921.43	$921.45	$921.30