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	$181.42	6.317%	$192.8803	$192.88	$192.90	$192.90
Purchase #2	$63.85	11.561%	$71.2317	$71.23	$71.25	$71.20
Purchase #3	$147.57	12.668%	$166.2642	$166.26	$166.25	$166.30
Purchase #4	$15.74	5.449%	$16.5977	$16.60	$16.60	$16.60
Purchase #5	$207.92	11.240%	$231.2902	$231.29	$231.30	$231.30
Purchase #6	$205.55	5.516%	$216.8881	$216.89	$216.90	$216.90
Purchase #7	$87.32	13.638%	$99.2287	$99.23	$99.25	$99.20
7 purchase totals =	$909.37		$994.3809	$994.38	$994.45	$994.40