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	$196.71	13.249%	$222.7721	$222.77	$222.75	$222.80
Purchase #2	$227.43	9.727%	$249.5521	$249.55	$249.55	$249.60
Purchase #3	$190.49	10.575%	$210.6343	$210.63	$210.65	$210.60
Purchase #4	$20.54	9.365%	$22.4636	$22.46	$22.45	$22.50
Purchase #5	$142.51	3.278%	$147.1815	$147.18	$147.20	$147.20
Purchase #6	$186.98	4.206%	$194.8444	$194.84	$194.85	$194.80
Purchase #7	$153.59	9.571%	$168.2901	$168.29	$168.30	$168.30
7 purchase totals =	$1,118.25		$1,215.7381	$1,215.72	$1,215.75	$1,215.80