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	$116.71	10.621%	$129.1058	$129.11	$129.10	$129.10
Purchase #2	$29.60	12.378%	$33.2639	$33.26	$33.25	$33.30
Purchase #3	$6.86	11.394%	$7.6416	$7.64	$7.65	$7.60
Purchase #4	$176.44	5.309%	$185.8072	$185.81	$185.80	$185.80
Purchase #5	$207.74	12.586%	$233.8862	$233.89	$233.90	$233.90
Purchase #6	$37.63	7.698%	$40.5268	$40.53	$40.55	$40.50
Purchase #7	$151.55	3.136%	$156.3026	$156.30	$156.30	$156.30
7 purchase totals =	$726.53		$786.5341	$786.54	$786.55	$786.50