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	$133.31	10.273%	$147.0049	$147.00	$147.00	$147.00
Purchase #2	$113.35	4.538%	$118.4938	$118.49	$118.50	$118.50
Purchase #3	$91.32	7.780%	$98.4247	$98.42	$98.40	$98.40
Purchase #4	$174.38	6.122%	$185.0555	$185.06	$185.05	$185.10
Purchase #5	$162.89	13.622%	$185.0789	$185.08	$185.10	$185.10
Purchase #6	$157.56	3.239%	$162.6634	$162.66	$162.65	$162.70
Purchase #7	$64.75	9.807%	$71.1	$71.10	$71.10	$71.10
7 purchase totals =	$897.56		$967.8212	$967.81	$967.80	$967.90