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	$101.43	3.128%	$104.6027	$104.60	$104.60	$104.60
Purchase #2	$143.67	3.694%	$148.9772	$148.98	$149.00	$149.00
Purchase #3	$122.38	3.221%	$126.3219	$126.32	$126.30	$126.30
Purchase #4	$159.48	5.453%	$168.1764	$168.18	$168.20	$168.20
Purchase #5	$240.72	9.843%	$264.4141	$264.41	$264.40	$264.40
Purchase #6	$90.69	10.397%	$100.119	$100.12	$100.10	$100.10
Purchase #7	$14.59	6.575%	$15.5493	$15.55	$15.55	$15.50
7 purchase totals =	$872.96		$928.1606	$928.16	$928.15	$928.10