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	$192.88	9.213%	$210.65	$210.65	$210.65	$210.70
Purchase #2	$100.65	4.201%	$104.8783	$104.88	$104.90	$104.90
Purchase #3	$167.89	4.203%	$174.9464	$174.95	$174.95	$174.90
Purchase #4	$62.25	6.581%	$66.3467	$66.35	$66.35	$66.30
Purchase #5	$199.72	11.124%	$221.9369	$221.94	$221.95	$221.90
Purchase #6	$140.39	8.191%	$151.8893	$151.89	$151.90	$151.90
Purchase #7	$42.32	4.633%	$44.2807	$44.28	$44.30	$44.30
7 purchase totals =	$906.10		$974.9283	$974.94	$975.00	$974.90