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	$241.50	7.462%	$259.5207	$259.52	$259.50	$259.50
Purchase #2	$163.81	6.724%	$174.8246	$174.82	$174.80	$174.80
Purchase #3	$7.72	7.803%	$8.3224	$8.32	$8.30	$8.30
Purchase #4	$84.85	6.644%	$90.4874	$90.49	$90.50	$90.50
Purchase #5	$57.38	5.287%	$60.4137	$60.41	$60.40	$60.40
Purchase #6	$152.54	12.502%	$171.6106	$171.61	$171.60	$171.60
Purchase #7	$153.94	5.734%	$162.7669	$162.77	$162.75	$162.80
7 purchase totals =	$861.74		$927.9463	$927.94	$927.85	$927.90