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	$42.88	10.549%	$47.4034	$47.40	$47.40	$47.40
Purchase #2	$200.44	11.325%	$223.1398	$223.14	$223.15	$223.10
Purchase #3	$133.62	5.561%	$141.0506	$141.05	$141.05	$141.10
Purchase #4	$113.93	11.812%	$127.3874	$127.39	$127.40	$127.40
Purchase #5	$115.45	4.689%	$120.8635	$120.86	$120.85	$120.90
Purchase #6	$171.91	3.754%	$178.3635	$178.36	$178.35	$178.40
Purchase #7	$224.50	13.845%	$255.582	$255.58	$255.60	$255.60
7 purchase totals =	$1,002.73		$1,093.7902	$1,093.78	$1,093.80	$1,093.90