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	$89.43	6.345%	$95.1043	$95.10	$95.10	$95.10
Purchase #2	$111.38	7.106%	$119.2947	$119.29	$119.30	$119.30
Purchase #3	$186.49	11.678%	$208.2683	$208.27	$208.25	$208.30
Purchase #4	$83.55	4.675%	$87.456	$87.46	$87.45	$87.50
Purchase #5	$143.78	6.786%	$153.5369	$153.54	$153.55	$153.50
Purchase #6	$71.60	3.254%	$73.9299	$73.93	$73.95	$73.90
Purchase #7	$160.47	9.350%	$175.4739	$175.47	$175.45	$175.50
7 purchase totals =	$846.70		$913.0640	$913.06	$913.05	$913.10