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	$109.69	4.691%	$114.8356	$114.84	$114.85	$114.80
Purchase #2	$90.35	10.871%	$100.1719	$100.17	$100.15	$100.20
Purchase #3	$38.67	12.753%	$43.6016	$43.60	$43.60	$43.60
Purchase #4	$67.30	6.516%	$71.6853	$71.69	$71.70	$71.70
Purchase #5	$201.89	13.147%	$228.4325	$228.43	$228.45	$228.40
Purchase #6	$79.80	8.378%	$86.4856	$86.49	$86.50	$86.50
Purchase #7	$162.37	13.470%	$184.2412	$184.24	$184.25	$184.20
7 purchase totals =	$750.07		$829.4537	$829.46	$829.50	$829.40