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	$204.59	10.223%	$225.5052	$225.51	$225.50	$225.50
Purchase #2	$183.26	6.186%	$194.5965	$194.60	$194.60	$194.60
Purchase #3	$54.70	5.678%	$57.8059	$57.81	$57.80	$57.80
Purchase #4	$171.43	3.376%	$177.2175	$177.22	$177.20	$177.20
Purchase #5	$194.41	7.820%	$209.6129	$209.61	$209.60	$209.60
Purchase #6	$35.33	5.658%	$37.329	$37.33	$37.35	$37.30
Purchase #7	$239.80	3.641%	$248.5311	$248.53	$248.55	$248.50
7 purchase totals =	$1,083.52		$1,150.5981	$1,150.61	$1,150.60	$1,150.50