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	$141.26	9.102%	$154.1175	$154.12	$154.10	$154.10
Purchase #2	$146.77	6.393%	$156.153	$156.15	$156.15	$156.20
Purchase #3	$230.42	4.858%	$241.6138	$241.61	$241.60	$241.60
Purchase #4	$197.74	6.138%	$209.8773	$209.88	$209.90	$209.90
Purchase #5	$153.69	12.245%	$172.5093	$172.51	$172.50	$172.50
Purchase #6	$111.76	3.610%	$115.7945	$115.79	$115.80	$115.80
Purchase #7	$77.92	3.807%	$80.8864	$80.89	$80.90	$80.90
7 purchase totals =	$1,059.56		$1,130.9518	$1,130.95	$1,130.95	$1,131.00