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	$73.94	11.260%	$82.2656	$82.27	$82.25	$82.30
Purchase #2	$241.75	5.390%	$254.7803	$254.78	$254.80	$254.80
Purchase #3	$98.91	11.742%	$110.524	$110.52	$110.50	$110.50
Purchase #4	$43.25	12.229%	$48.539	$48.54	$48.55	$48.50
Purchase #5	$248.91	5.401%	$262.3536	$262.35	$262.35	$262.40
Purchase #6	$156.52	7.747%	$168.6456	$168.65	$168.65	$168.60
Purchase #7	$169.47	13.735%	$192.7467	$192.75	$192.75	$192.70
7 purchase totals =	$1,032.75		$1,119.8548	$1,119.86	$1,119.85	$1,119.80