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	$95.89	13.734%	$109.0595	$109.06	$109.05	$109.10
Purchase #2	$240.29	3.333%	$248.2989	$248.30	$248.30	$248.30
Purchase #3	$240.44	3.259%	$248.2759	$248.28	$248.30	$248.30
Purchase #4	$210.72	11.800%	$235.585	$235.59	$235.60	$235.60
Purchase #5	$35.49	12.658%	$39.9823	$39.98	$40.00	$40.00
Purchase #6	$137.31	11.687%	$153.3574	$153.36	$153.35	$153.40
Purchase #7	$200.85	9.765%	$220.463	$220.46	$220.45	$220.50
7 purchase totals =	$1,160.99		$1,255.0220	$1,255.03	$1,255.05	$1,255.20