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	$75.53	13.834%	$85.9788	$85.98	$86.00	$86.00
Purchase #2	$98.36	7.732%	$105.9652	$105.97	$105.95	$106.00
Purchase #3	$101.43	7.547%	$109.0849	$109.08	$109.10	$109.10
Purchase #4	$74.81	10.179%	$82.4249	$82.42	$82.40	$82.40
Purchase #5	$137.57	9.539%	$150.6928	$150.69	$150.70	$150.70
Purchase #6	$31.94	6.125%	$33.8963	$33.90	$33.90	$33.90
Purchase #7	$109.57	3.596%	$113.5101	$113.51	$113.50	$113.50
7 purchase totals =	$629.21		$681.5530	$681.55	$681.55	$681.60