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	$72.47	7.832%	$78.1459	$78.15	$78.15	$78.10
Purchase #2	$175.32	3.298%	$181.1021	$181.10	$181.10	$181.10
Purchase #3	$247.50	5.446%	$260.9789	$260.98	$261.00	$261.00
Purchase #4	$63.42	12.201%	$71.1579	$71.16	$71.15	$71.20
Purchase #5	$34.91	8.525%	$37.8861	$37.89	$37.90	$37.90
Purchase #6	$103.35	5.648%	$109.1872	$109.19	$109.20	$109.20
Purchase #7	$152.38	4.331%	$158.9796	$158.98	$159.00	$159.00
7 purchase totals =	$849.35		$897.4377	$897.45	$897.50	$897.50