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	$210.89	8.379%	$228.5605	$228.56	$228.55	$228.60
Purchase #2	$12.36	7.356%	$13.2692	$13.27	$13.25	$13.30
Purchase #3	$96.29	4.222%	$100.3554	$100.36	$100.35	$100.40
Purchase #4	$242.54	9.769%	$266.2337	$266.23	$266.25	$266.20
Purchase #5	$110.96	4.548%	$116.0065	$116.01	$116.00	$116.00
Purchase #6	$105.99	5.166%	$111.4654	$111.47	$111.45	$111.50
Purchase #7	$108.35	9.682%	$118.8404	$118.84	$118.85	$118.80
7 purchase totals =	$887.38		$954.7311	$954.74	$954.70	$954.80