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	$152.55	6.578%	$162.5847	$162.58	$162.60	$162.60
Purchase #2	$39.62	6.792%	$42.311	$42.31	$42.30	$42.30
Purchase #3	$61.78	13.376%	$70.0437	$70.04	$70.05	$70.00
Purchase #4	$14.28	7.547%	$15.3577	$15.36	$15.35	$15.40
Purchase #5	$65.44	11.593%	$73.0265	$73.03	$73.05	$73.00
Purchase #6	$12.32	12.716%	$13.8866	$13.89	$13.90	$13.90
Purchase #7	$105.80	13.194%	$119.7593	$119.76	$119.75	$119.80
7 purchase totals =	$451.79		$496.9695	$496.97	$497.00	$497.00