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	$61.56	4.507%	$64.3345	$64.33	$64.35	$64.30
Purchase #2	$148.32	7.576%	$159.5567	$159.56	$159.55	$159.60
Purchase #3	$219.31	8.674%	$238.3329	$238.33	$238.35	$238.30
Purchase #4	$170.86	12.645%	$192.4652	$192.47	$192.45	$192.50
Purchase #5	$221.29	8.689%	$240.5179	$240.52	$240.50	$240.50
Purchase #6	$154.77	7.575%	$166.4938	$166.49	$166.50	$166.50
Purchase #7	$11.82	11.810%	$13.2159	$13.22	$13.20	$13.20
7 purchase totals =	$987.93		$1,074.9169	$1,074.92	$1,074.90	$1,074.90