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	$47.89	10.144%	$52.748	$52.75	$52.75	$52.70
Purchase #2	$208.60	6.561%	$222.2862	$222.29	$222.30	$222.30
Purchase #3	$24.28	6.823%	$25.9366	$25.94	$25.95	$25.90
Purchase #4	$18.82	10.248%	$20.7487	$20.75	$20.75	$20.70
Purchase #5	$37.46	9.402%	$40.982	$40.98	$41.00	$41.00
Purchase #6	$181.72	13.241%	$205.7815	$205.78	$205.80	$205.80
Purchase #7	$141.33	12.445%	$158.9185	$158.92	$158.90	$158.90
7 purchase totals =	$660.10		$727.4015	$727.41	$727.45	$727.30