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	$131.37	8.542%	$142.5916	$142.59	$142.60	$142.60
Purchase #2	$127.91	10.716%	$141.6168	$141.62	$141.60	$141.60
Purchase #3	$55.79	8.164%	$60.3447	$60.34	$60.35	$60.30
Purchase #4	$62.36	5.683%	$65.9039	$65.90	$65.90	$65.90
Purchase #5	$204.35	5.868%	$216.3413	$216.34	$216.35	$216.30
Purchase #6	$224.33	7.702%	$241.6079	$241.61	$241.60	$241.60
Purchase #7	$77.92	5.341%	$82.0817	$82.08	$82.10	$82.10
7 purchase totals =	$884.03		$950.4879	$950.48	$950.50	$950.40