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	$78.80	10.333%	$86.9424	$86.94	$86.95	$86.90
Purchase #2	$83.56	9.251%	$91.2901	$91.29	$91.30	$91.30
Purchase #3	$188.66	10.235%	$207.9694	$207.97	$207.95	$208.00
Purchase #4	$128.67	11.837%	$143.9007	$143.90	$143.90	$143.90
Purchase #5	$113.88	11.575%	$127.0616	$127.06	$127.05	$127.10
Purchase #6	$99.78	7.505%	$107.2685	$107.27	$107.25	$107.30
Purchase #7	$32.57	12.162%	$36.5312	$36.53	$36.55	$36.50
7 purchase totals =	$725.92		$800.9639	$800.96	$800.95	$801.00