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	$111.99	6.360%	$119.1126	$119.11	$119.10	$119.10
Purchase #2	$225.77	10.871%	$250.3135	$250.31	$250.30	$250.30
Purchase #3	$182.47	3.627%	$189.0882	$189.09	$189.10	$189.10
Purchase #4	$15.35	3.346%	$15.8636	$15.86	$15.85	$15.90
Purchase #5	$143.96	4.526%	$150.4756	$150.48	$150.50	$150.50
Purchase #6	$31.35	13.276%	$35.512	$35.51	$35.50	$35.50
Purchase #7	$180.45	3.389%	$186.5655	$186.57	$186.55	$186.60
7 purchase totals =	$891.34		$946.9310	$946.93	$946.90	$947.00