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	$171.34	4.826%	$179.6089	$179.61	$179.60	$179.60
Purchase #2	$146.58	5.283%	$154.3238	$154.32	$154.30	$154.30
Purchase #3	$116.74	7.452%	$125.4395	$125.44	$125.45	$125.40
Purchase #4	$223.76	8.695%	$243.2159	$243.22	$243.20	$243.20
Purchase #5	$57.96	4.739%	$60.7067	$60.71	$60.70	$60.70
Purchase #6	$86.90	4.307%	$90.6428	$90.64	$90.65	$90.60
Purchase #7	$197.59	5.213%	$207.8904	$207.89	$207.90	$207.90
7 purchase totals =	$1,000.87		$1,061.8280	$1,061.83	$1,061.80	$1,061.70