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	$113.83	4.616%	$119.0844	$119.08	$119.10	$119.10
Purchase #2	$115.88	13.650%	$131.6976	$131.70	$131.70	$131.70
Purchase #3	$172.29	9.204%	$188.1476	$188.15	$188.15	$188.10
Purchase #4	$165.64	8.856%	$180.3091	$180.31	$180.30	$180.30
Purchase #5	$32.45	9.398%	$35.4997	$35.50	$35.50	$35.50
Purchase #6	$9.29	11.153%	$10.3261	$10.33	$10.35	$10.30
Purchase #7	$150.99	8.643%	$164.0401	$164.04	$164.05	$164.00
7 purchase totals =	$760.37		$829.1046	$829.11	$829.15	$829.00