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	$90.94	7.791%	$98.0251	$98.03	$98.05	$98.00
Purchase #2	$160.94	12.397%	$180.8917	$180.89	$180.90	$180.90
Purchase #3	$210.82	3.490%	$218.1776	$218.18	$218.20	$218.20
Purchase #4	$39.82	6.632%	$42.4609	$42.46	$42.45	$42.50
Purchase #5	$160.40	12.750%	$180.851	$180.85	$180.85	$180.90
Purchase #6	$157.32	8.200%	$170.2202	$170.22	$170.20	$170.20
Purchase #7	$38.51	6.212%	$40.9022	$40.90	$40.90	$40.90
7 purchase totals =	$858.75		$931.5287	$931.53	$931.55	$931.60