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	$52.88	8.500%	$57.3748	$57.37	$57.35	$57.40
Purchase #2	$64.58	12.297%	$72.5214	$72.52	$72.50	$72.50
Purchase #3	$65.71	8.582%	$71.3492	$71.35	$71.35	$71.30
Purchase #4	$68.96	4.413%	$72.0032	$72.00	$72.00	$72.00
Purchase #5	$197.54	8.490%	$214.3111	$214.31	$214.30	$214.30
Purchase #6	$157.81	6.698%	$168.3801	$168.38	$168.40	$168.40
Purchase #7	$56.71	5.387%	$59.765	$59.77	$59.75	$59.80
7 purchase totals =	$664.19		$715.7048	$715.70	$715.65	$715.70