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	$95.87	11.678%	$107.0657	$107.07	$107.05	$107.10
Purchase #2	$78.78	4.775%	$82.5417	$82.54	$82.55	$82.50
Purchase #3	$154.54	10.693%	$171.065	$171.07	$171.05	$171.10
Purchase #4	$110.39	8.347%	$119.6043	$119.60	$119.60	$119.60
Purchase #5	$153.62	11.528%	$171.3293	$171.33	$171.35	$171.30
Purchase #6	$159.96	7.143%	$171.3859	$171.39	$171.40	$171.40
Purchase #7	$214.51	6.553%	$228.5668	$228.57	$228.55	$228.60
7 purchase totals =	$967.67		$1,051.5587	$1,051.57	$1,051.55	$1,051.60