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	$119.73	12.274%	$134.4257	$134.43	$134.45	$134.40
Purchase #2	$118.41	10.719%	$131.1024	$131.10	$131.10	$131.10
Purchase #3	$40.56	8.362%	$43.9516	$43.95	$43.95	$44.00
Purchase #4	$71.73	6.773%	$76.5883	$76.59	$76.60	$76.60
Purchase #5	$41.36	3.236%	$42.6984	$42.70	$42.70	$42.70
Purchase #6	$188.57	13.215%	$213.4895	$213.49	$213.50	$213.50
Purchase #7	$211.55	13.743%	$240.6233	$240.62	$240.60	$240.60
7 purchase totals =	$791.91		$882.8792	$882.88	$882.90	$882.90