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	$151.94	5.133%	$159.7391	$159.74	$159.75	$159.70
Purchase #2	$81.74	4.633%	$85.527	$85.53	$85.55	$85.50
Purchase #3	$36.37	10.173%	$40.0699	$40.07	$40.05	$40.10
Purchase #4	$110.60	5.651%	$116.85	$116.85	$116.85	$116.90
Purchase #5	$168.42	8.527%	$182.7812	$182.78	$182.80	$182.80
Purchase #6	$127.42	7.502%	$136.979	$136.98	$137.00	$137.00
Purchase #7	$156.91	4.726%	$164.3256	$164.33	$164.35	$164.30
7 purchase totals =	$833.40		$886.2718	$886.28	$886.35	$886.30