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	$208.85	11.862%	$233.6238	$233.62	$233.60	$233.60
Purchase #2	$142.87	9.258%	$156.0969	$156.10	$156.10	$156.10
Purchase #3	$55.63	10.240%	$61.3265	$61.33	$61.35	$61.30
Purchase #4	$170.70	10.733%	$189.0212	$189.02	$189.00	$189.00
Purchase #5	$76.96	3.102%	$79.3473	$79.35	$79.35	$79.30
Purchase #6	$238.67	12.667%	$268.9023	$268.90	$268.90	$268.90
Purchase #7	$18.78	9.405%	$20.5463	$20.55	$20.55	$20.50
7 purchase totals =	$912.46		$1,008.8643	$1,008.87	$1,008.85	$1,008.70