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	$211.67	5.142%	$222.5541	$222.55	$222.55	$222.60
Purchase #2	$131.71	6.788%	$140.6505	$140.65	$140.65	$140.70
Purchase #3	$108.91	3.819%	$113.0693	$113.07	$113.05	$113.10
Purchase #4	$179.27	6.183%	$190.3543	$190.35	$190.35	$190.40
Purchase #5	$39.25	8.272%	$42.4968	$42.50	$42.50	$42.50
Purchase #6	$164.35	12.812%	$185.4065	$185.41	$185.40	$185.40
Purchase #7	$222.85	8.782%	$242.4207	$242.42	$242.40	$242.40
7 purchase totals =	$1,058.01		$1,136.9522	$1,136.95	$1,136.90	$1,137.10