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	$225.52	9.389%	$246.6941	$246.69	$246.70	$246.70
Purchase #2	$208.66	11.254%	$232.1426	$232.14	$232.15	$232.10
Purchase #3	$240.75	9.725%	$264.1629	$264.16	$264.15	$264.20
Purchase #4	$109.93	12.404%	$123.5657	$123.57	$123.55	$123.60
Purchase #5	$32.75	9.159%	$35.7496	$35.75	$35.75	$35.70
Purchase #6	$103.92	6.838%	$111.026	$111.03	$111.05	$111.00
Purchase #7	$72.99	12.835%	$82.3583	$82.36	$82.35	$82.40
7 purchase totals =	$994.52		$1,095.6992	$1,095.70	$1,095.70	$1,095.70