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	$75.91	9.469%	$83.0979	$83.10	$83.10	$83.10
Purchase #2	$145.48	6.444%	$154.8547	$154.85	$154.85	$154.90
Purchase #3	$243.29	7.646%	$261.892	$261.89	$261.90	$261.90
Purchase #4	$95.85	6.795%	$102.363	$102.36	$102.35	$102.40
Purchase #5	$49.60	9.199%	$54.1627	$54.16	$54.15	$54.20
Purchase #6	$143.42	10.729%	$158.8075	$158.81	$158.80	$158.80
Purchase #7	$250.61	6.641%	$267.253	$267.25	$267.25	$267.30
7 purchase totals =	$1,004.16		$1,082.4308	$1,082.42	$1,082.40	$1,082.60