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	$108.87	4.632%	$113.9129	$113.91	$113.90	$113.90
Purchase #2	$71.54	12.134%	$80.2207	$80.22	$80.20	$80.20
Purchase #3	$210.57	3.597%	$218.1442	$218.14	$218.15	$218.10
Purchase #4	$73.66	9.811%	$80.8868	$80.89	$80.90	$80.90
Purchase #5	$227.95	3.798%	$236.6075	$236.61	$236.60	$236.60
Purchase #6	$182.48	12.246%	$204.8265	$204.83	$204.85	$204.80
Purchase #7	$66.89	6.718%	$71.3837	$71.38	$71.40	$71.40
7 purchase totals =	$941.96		$1,005.9823	$1,005.98	$1,006.00	$1,005.90