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	$191.77	8.223%	$207.5392	$207.54	$207.55	$207.50
Purchase #2	$43.72	11.180%	$48.6079	$48.61	$48.60	$48.60
Purchase #3	$10.78	7.497%	$11.5882	$11.59	$11.60	$11.60
Purchase #4	$195.90	6.483%	$208.6002	$208.60	$208.60	$208.60
Purchase #5	$194.37	6.517%	$207.0371	$207.04	$207.05	$207.00
Purchase #6	$78.46	8.450%	$85.0899	$85.09	$85.10	$85.10
Purchase #7	$230.28	3.610%	$238.5931	$238.59	$238.60	$238.60
7 purchase totals =	$945.28		$1,007.0556	$1,007.06	$1,007.10	$1,007.00