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	$174.87	9.139%	$190.8514	$190.85	$190.85	$190.90
Purchase #2	$111.39	7.360%	$119.5883	$119.59	$119.60	$119.60
Purchase #3	$33.58	5.864%	$35.5491	$35.55	$35.55	$35.50
Purchase #4	$195.51	13.759%	$222.4102	$222.41	$222.40	$222.40
Purchase #5	$242.48	10.119%	$267.0166	$267.02	$267.00	$267.00
Purchase #6	$198.58	12.300%	$223.0053	$223.01	$223.00	$223.00
Purchase #7	$7.28	13.812%	$8.2855	$8.29	$8.30	$8.30
7 purchase totals =	$963.69		$1,066.7064	$1,066.72	$1,066.70	$1,066.70