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	$170.36	6.279%	$181.0569	$181.06	$181.05	$181.10
Purchase #2	$6.88	10.491%	$7.6018	$7.60	$7.60	$7.60
Purchase #3	$108.33	3.689%	$112.3263	$112.33	$112.35	$112.30
Purchase #4	$12.42	7.661%	$13.3715	$13.37	$13.35	$13.40
Purchase #5	$81.85	10.720%	$90.6243	$90.62	$90.60	$90.60
Purchase #6	$96.55	4.604%	$100.9952	$101.00	$101.00	$101.00
Purchase #7	$54.89	4.272%	$57.2349	$57.23	$57.25	$57.20
7 purchase totals =	$531.28		$563.2109	$563.21	$563.20	$563.20