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	$83.49	7.154%	$89.4629	$89.46	$89.45	$89.50
Purchase #2	$197.67	9.747%	$216.9369	$216.94	$216.95	$216.90
Purchase #3	$57.82	5.377%	$60.929	$60.93	$60.95	$60.90
Purchase #4	$188.66	8.608%	$204.8999	$204.90	$204.90	$204.90
Purchase #5	$229.96	13.720%	$261.5105	$261.51	$261.50	$261.50
Purchase #6	$37.69	12.677%	$42.468	$42.47	$42.45	$42.50
Purchase #7	$204.85	6.463%	$218.0895	$218.09	$218.10	$218.10
7 purchase totals =	$1,000.14		$1,094.2967	$1,094.30	$1,094.30	$1,094.30