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	$207.70	7.677%	$223.6451	$223.65	$223.65	$223.60
Purchase #2	$94.42	6.724%	$100.7688	$100.77	$100.75	$100.80
Purchase #3	$143.65	10.327%	$158.4847	$158.48	$158.50	$158.50
Purchase #4	$157.91	7.856%	$170.3154	$170.32	$170.30	$170.30
Purchase #5	$195.99	9.112%	$213.8486	$213.85	$213.85	$213.80
Purchase #6	$191.67	7.648%	$206.3289	$206.33	$206.35	$206.30
Purchase #7	$11.59	11.216%	$12.8899	$12.89	$12.90	$12.90
7 purchase totals =	$1,002.93		$1,086.2814	$1,086.29	$1,086.30	$1,086.20