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	$153.57	3.482%	$158.9173	$158.92	$158.90	$158.90
Purchase #2	$40.99	10.353%	$45.2337	$45.23	$45.25	$45.20
Purchase #3	$146.53	11.109%	$162.808	$162.81	$162.80	$162.80
Purchase #4	$205.44	9.559%	$225.078	$225.08	$225.10	$225.10
Purchase #5	$221.74	8.604%	$240.8185	$240.82	$240.80	$240.80
Purchase #6	$187.63	12.393%	$210.883	$210.88	$210.90	$210.90
Purchase #7	$52.70	8.633%	$57.2496	$57.25	$57.25	$57.20
7 purchase totals =	$1,008.60		$1,100.9881	$1,100.99	$1,101.00	$1,100.90