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	$228.78	6.527%	$243.7125	$243.71	$243.70	$243.70
Purchase #2	$144.93	4.172%	$150.9765	$150.98	$151.00	$151.00
Purchase #3	$147.39	7.171%	$157.9593	$157.96	$157.95	$158.00
Purchase #4	$84.77	9.143%	$92.5205	$92.52	$92.50	$92.50
Purchase #5	$118.32	7.342%	$127.0071	$127.01	$127.00	$127.00
Purchase #6	$55.89	3.426%	$57.8048	$57.80	$57.80	$57.80
Purchase #7	$90.88	13.587%	$103.2279	$103.23	$103.25	$103.20
7 purchase totals =	$870.96		$933.2086	$933.21	$933.20	$933.20