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	$114.34	13.753%	$130.0652	$130.07	$130.05	$130.10
Purchase #2	$58.54	4.854%	$61.3815	$61.38	$61.40	$61.40
Purchase #3	$114.81	10.466%	$126.826	$126.83	$126.85	$126.80
Purchase #4	$143.71	5.280%	$151.2979	$151.30	$151.30	$151.30
Purchase #5	$32.91	10.372%	$36.3234	$36.32	$36.30	$36.30
Purchase #6	$76.43	12.578%	$86.0434	$86.04	$86.05	$86.00
Purchase #7	$94.36	10.129%	$103.9177	$103.92	$103.90	$103.90
7 purchase totals =	$635.10		$695.8551	$695.86	$695.85	$695.80