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	$53.99	10.418%	$59.6147	$59.61	$59.60	$59.60
Purchase #2	$156.96	7.423%	$168.6111	$168.61	$168.60	$168.60
Purchase #3	$94.88	11.720%	$105.9999	$106.00	$106.00	$106.00
Purchase #4	$137.59	4.463%	$143.7306	$143.73	$143.75	$143.70
Purchase #5	$87.70	9.587%	$96.1078	$96.11	$96.10	$96.10
Purchase #6	$113.92	9.456%	$124.6923	$124.69	$124.70	$124.70
Purchase #7	$31.82	3.348%	$32.8853	$32.89	$32.90	$32.90
7 purchase totals =	$676.86		$731.6417	$731.64	$731.65	$731.60