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	$233.86	13.811%	$266.1584	$266.16	$266.15	$266.20
Purchase #2	$35.83	7.588%	$38.5488	$38.55	$38.55	$38.50
Purchase #3	$209.87	11.687%	$234.3975	$234.40	$234.40	$234.40
Purchase #4	$94.57	4.484%	$98.8105	$98.81	$98.80	$98.80
Purchase #5	$19.30	4.153%	$20.1015	$20.10	$20.10	$20.10
Purchase #6	$182.72	8.148%	$197.608	$197.61	$197.60	$197.60
Purchase #7	$210.40	11.158%	$233.8764	$233.88	$233.90	$233.90
7 purchase totals =	$986.55		$1,089.5011	$1,089.51	$1,089.50	$1,089.50