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	$61.63	5.316%	$64.9063	$64.91	$64.90	$64.90
Purchase #2	$107.99	11.336%	$120.2317	$120.23	$120.25	$120.20
Purchase #3	$55.93	8.698%	$60.7948	$60.79	$60.80	$60.80
Purchase #4	$226.41	12.804%	$255.3995	$255.40	$255.40	$255.40
Purchase #5	$81.58	10.298%	$89.9811	$89.98	$90.00	$90.00
Purchase #6	$168.94	6.653%	$180.1796	$180.18	$180.20	$180.20
Purchase #7	$170.89	11.702%	$190.8875	$190.89	$190.90	$190.90
7 purchase totals =	$873.37		$962.3805	$962.38	$962.45	$962.40