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	$115.89	8.128%	$125.3095	$125.31	$125.30	$125.30
Purchase #2	$90.79	5.843%	$96.0949	$96.09	$96.10	$96.10
Purchase #3	$104.98	12.128%	$117.712	$117.71	$117.70	$117.70
Purchase #4	$244.37	3.719%	$253.4581	$253.46	$253.45	$253.50
Purchase #5	$250.89	6.347%	$266.814	$266.81	$266.80	$266.80
Purchase #6	$163.35	6.851%	$174.5411	$174.54	$174.55	$174.50
Purchase #7	$40.66	4.612%	$42.5352	$42.54	$42.55	$42.50
7 purchase totals =	$1,010.93		$1,076.4648	$1,076.46	$1,076.45	$1,076.40