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	$175.88	5.719%	$185.9386	$185.94	$185.95	$185.90
Purchase #2	$209.33	4.807%	$219.3925	$219.39	$219.40	$219.40
Purchase #3	$101.94	11.357%	$113.5173	$113.52	$113.50	$113.50
Purchase #4	$48.96	13.790%	$55.7116	$55.71	$55.70	$55.70
Purchase #5	$199.36	7.134%	$213.5823	$213.58	$213.60	$213.60
Purchase #6	$50.99	7.316%	$54.7204	$54.72	$54.70	$54.70
Purchase #7	$228.67	11.600%	$255.1957	$255.20	$255.20	$255.20
7 purchase totals =	$1,015.13		$1,098.0584	$1,098.06	$1,098.05	$1,098.00