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	$240.92	9.687%	$264.2579	$264.26	$264.25	$264.30
Purchase #2	$116.81	12.542%	$131.4603	$131.46	$131.45	$131.50
Purchase #3	$244.67	8.811%	$266.2279	$266.23	$266.25	$266.20
Purchase #4	$92.85	7.228%	$99.5612	$99.56	$99.55	$99.60
Purchase #5	$172.48	10.610%	$190.7801	$190.78	$190.80	$190.80
Purchase #6	$191.60	6.379%	$203.8222	$203.82	$203.80	$203.80
Purchase #7	$114.40	3.660%	$118.587	$118.59	$118.60	$118.60
7 purchase totals =	$1,173.73		$1,274.6966	$1,274.70	$1,274.70	$1,274.80