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	$82.53	4.636%	$86.3561	$86.36	$86.35	$86.40
Purchase #2	$49.89	11.825%	$55.7895	$55.79	$55.80	$55.80
Purchase #3	$162.38	12.795%	$183.1565	$183.16	$183.15	$183.20
Purchase #4	$115.55	10.630%	$127.833	$127.83	$127.85	$127.80
Purchase #5	$161.81	8.855%	$176.1383	$176.14	$176.15	$176.10
Purchase #6	$69.47	13.110%	$78.5775	$78.58	$78.60	$78.60
Purchase #7	$181.90	4.698%	$190.4457	$190.45	$190.45	$190.40
7 purchase totals =	$823.53		$898.2966	$898.31	$898.35	$898.30