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	$30.97	3.431%	$32.0326	$32.03	$32.05	$32.00
Purchase #2	$171.40	8.774%	$186.4386	$186.44	$186.45	$186.40
Purchase #3	$120.93	5.471%	$127.5461	$127.55	$127.55	$127.50
Purchase #4	$226.52	4.705%	$237.1778	$237.18	$237.20	$237.20
Purchase #5	$176.37	11.150%	$196.0353	$196.04	$196.05	$196.00
Purchase #6	$217.92	7.359%	$233.9567	$233.96	$233.95	$234.00
Purchase #7	$45.37	5.874%	$48.035	$48.04	$48.05	$48.00
7 purchase totals =	$989.48		$1,061.2221	$1,061.24	$1,061.30	$1,061.10