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	$197.54	13.419%	$224.0479	$224.05	$224.05	$224.00
Purchase #2	$38.45	11.868%	$43.0132	$43.01	$43.00	$43.00
Purchase #3	$43.43	4.291%	$45.2936	$45.29	$45.30	$45.30
Purchase #4	$55.74	7.523%	$59.9333	$59.93	$59.95	$59.90
Purchase #5	$167.70	8.690%	$182.2731	$182.27	$182.25	$182.30
Purchase #6	$70.97	12.785%	$80.0435	$80.04	$80.05	$80.00
Purchase #7	$234.85	5.774%	$248.4102	$248.41	$248.40	$248.40
7 purchase totals =	$808.68		$883.0148	$883.00	$883.00	$882.90