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	$73.89	4.182%	$76.9801	$76.98	$77.00	$77.00
Purchase #2	$35.78	12.491%	$40.2493	$40.25	$40.25	$40.20
Purchase #3	$191.67	8.183%	$207.3544	$207.35	$207.35	$207.40
Purchase #4	$191.65	8.814%	$208.542	$208.54	$208.55	$208.50
Purchase #5	$237.39	5.471%	$250.3776	$250.38	$250.40	$250.40
Purchase #6	$250.46	10.417%	$276.5504	$276.55	$276.55	$276.60
Purchase #7	$105.33	7.182%	$112.8948	$112.89	$112.90	$112.90
7 purchase totals =	$1,086.17		$1,172.9486	$1,172.94	$1,173.00	$1,173.00