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	$218.93	8.315%	$237.134	$237.13	$237.15	$237.10
Purchase #2	$211.46	5.354%	$222.7816	$222.78	$222.80	$222.80
Purchase #3	$72.66	8.216%	$78.6297	$78.63	$78.65	$78.60
Purchase #4	$136.65	7.157%	$146.43	$146.43	$146.45	$146.40
Purchase #5	$68.90	4.353%	$71.8992	$71.90	$71.90	$71.90
Purchase #6	$115.34	12.554%	$129.8198	$129.82	$129.80	$129.80
Purchase #7	$192.47	9.121%	$210.0252	$210.03	$210.05	$210.00
7 purchase totals =	$1,016.41		$1,096.7195	$1,096.72	$1,096.80	$1,096.60