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	$197.42	8.167%	$213.5433	$213.54	$213.55	$213.50
Purchase #2	$105.78	10.523%	$116.9112	$116.91	$116.90	$116.90
Purchase #3	$87.48	3.280%	$90.3493	$90.35	$90.35	$90.30
Purchase #4	$44.73	12.171%	$50.1741	$50.17	$50.15	$50.20
Purchase #5	$241.84	11.778%	$270.3239	$270.32	$270.30	$270.30
Purchase #6	$192.88	4.170%	$200.9231	$200.92	$200.90	$200.90
Purchase #7	$132.95	5.864%	$140.7462	$140.75	$140.75	$140.70
7 purchase totals =	$1,003.08		$1,082.9711	$1,082.96	$1,082.90	$1,082.80