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	$54.72	9.481%	$59.908	$59.91	$59.90	$59.90
Purchase #2	$8.97	11.627%	$10.0129	$10.01	$10.00	$10.00
Purchase #3	$58.98	12.819%	$66.5406	$66.54	$66.55	$66.50
Purchase #4	$152.96	9.142%	$166.9436	$166.94	$166.95	$166.90
Purchase #5	$47.96	11.813%	$53.6255	$53.63	$53.65	$53.60
Purchase #6	$60.72	12.781%	$68.4806	$68.48	$68.50	$68.50
Purchase #7	$163.87	13.232%	$185.5533	$185.55	$185.55	$185.60
7 purchase totals =	$548.18		$611.0645	$611.06	$611.10	$611.00