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	$136.59	8.712%	$148.4897	$148.49	$148.50	$148.50
Purchase #2	$70.33	10.443%	$77.6746	$77.67	$77.65	$77.70
Purchase #3	$35.90	11.488%	$40.0242	$40.02	$40.00	$40.00
Purchase #4	$218.51	10.459%	$241.364	$241.36	$241.35	$241.40
Purchase #5	$116.36	8.311%	$126.0307	$126.03	$126.05	$126.00
Purchase #6	$155.33	10.291%	$171.315	$171.32	$171.30	$171.30
Purchase #7	$244.93	5.443%	$258.2615	$258.26	$258.25	$258.30
7 purchase totals =	$977.95		$1,063.1597	$1,063.15	$1,063.10	$1,063.20