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	$147.96	5.760%	$156.4825	$156.48	$156.50	$156.50
Purchase #2	$112.30	10.824%	$124.4554	$124.46	$124.45	$124.50
Purchase #3	$65.51	4.749%	$68.6211	$68.62	$68.60	$68.60
Purchase #4	$89.55	11.213%	$99.5912	$99.59	$99.60	$99.60
Purchase #5	$244.82	7.253%	$262.5768	$262.58	$262.60	$262.60
Purchase #6	$18.81	11.265%	$20.9289	$20.93	$20.95	$20.90
Purchase #7	$238.81	9.644%	$261.8408	$261.84	$261.85	$261.80
7 purchase totals =	$917.76		$994.4967	$994.50	$994.55	$994.50