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	$161.54	12.173%	$181.2043	$181.20	$181.20	$181.20
Purchase #2	$119.94	8.240%	$129.8231	$129.82	$129.80	$129.80
Purchase #3	$37.93	11.653%	$42.35	$42.35	$42.35	$42.40
Purchase #4	$158.57	3.718%	$164.4656	$164.47	$164.45	$164.50
Purchase #5	$68.74	13.584%	$78.0776	$78.08	$78.10	$78.10
Purchase #6	$33.28	4.334%	$34.7224	$34.72	$34.70	$34.70
Purchase #7	$241.31	9.690%	$264.6929	$264.69	$264.70	$264.70
7 purchase totals =	$821.31		$895.3359	$895.33	$895.30	$895.40