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	$144.60	4.331%	$150.8626	$150.86	$150.85	$150.90
Purchase #2	$40.72	6.157%	$43.2271	$43.23	$43.25	$43.20
Purchase #3	$80.86	5.260%	$85.1132	$85.11	$85.10	$85.10
Purchase #4	$109.97	8.759%	$119.6023	$119.60	$119.60	$119.60
Purchase #5	$87.82	3.229%	$90.6557	$90.66	$90.65	$90.70
Purchase #6	$61.33	8.360%	$66.4572	$66.46	$66.45	$66.50
Purchase #7	$187.98	3.569%	$194.689	$194.69	$194.70	$194.70
7 purchase totals =	$713.28		$750.6071	$750.61	$750.60	$750.70