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	$76.88	8.220%	$83.1995	$83.20	$83.20	$83.20
Purchase #2	$249.64	6.596%	$266.1063	$266.11	$266.10	$266.10
Purchase #3	$176.25	12.745%	$198.7131	$198.71	$198.70	$198.70
Purchase #4	$34.31	3.462%	$35.4978	$35.50	$35.50	$35.50
Purchase #5	$82.26	10.515%	$90.9096	$90.91	$90.90	$90.90
Purchase #6	$171.58	11.673%	$191.6085	$191.61	$191.60	$191.60
Purchase #7	$167.83	8.716%	$182.4581	$182.46	$182.45	$182.50
7 purchase totals =	$958.75		$1,048.4929	$1,048.50	$1,048.45	$1,048.50