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	$153.36	4.443%	$160.1738	$160.17	$160.15	$160.20
Purchase #2	$157.88	9.687%	$173.1738	$173.17	$173.15	$173.20
Purchase #3	$126.30	9.453%	$138.2391	$138.24	$138.25	$138.20
Purchase #4	$132.51	6.459%	$141.0688	$141.07	$141.05	$141.10
Purchase #5	$75.58	8.641%	$82.1109	$82.11	$82.10	$82.10
Purchase #6	$118.41	11.844%	$132.4345	$132.43	$132.45	$132.40
Purchase #7	$75.27	4.825%	$78.9018	$78.90	$78.90	$78.90
7 purchase totals =	$839.31		$906.1027	$906.09	$906.05	$906.10