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	$184.77	5.411%	$194.7679	$194.77	$194.75	$194.80
Purchase #2	$30.62	13.820%	$34.8517	$34.85	$34.85	$34.90
Purchase #3	$215.38	11.551%	$240.2585	$240.26	$240.25	$240.30
Purchase #4	$101.55	6.665%	$108.3183	$108.32	$108.30	$108.30
Purchase #5	$55.50	7.268%	$59.5337	$59.53	$59.55	$59.50
Purchase #6	$228.98	12.606%	$257.8452	$257.85	$257.85	$257.80
Purchase #7	$196.86	13.429%	$223.2963	$223.30	$223.30	$223.30
7 purchase totals =	$1,013.66		$1,118.8716	$1,118.88	$1,118.85	$1,118.90