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	$76.81	11.284%	$85.4772	$85.48	$85.50	$85.50
Purchase #2	$30.34	3.741%	$31.475	$31.48	$31.50	$31.50
Purchase #3	$249.86	5.516%	$263.6423	$263.64	$263.65	$263.60
Purchase #4	$144.96	9.435%	$158.637	$158.64	$158.65	$158.60
Purchase #5	$202.82	6.299%	$215.5956	$215.60	$215.60	$215.60
Purchase #6	$209.82	9.682%	$230.1348	$230.13	$230.15	$230.10
Purchase #7	$56.71	12.157%	$63.6042	$63.60	$63.60	$63.60
7 purchase totals =	$971.32		$1,048.5661	$1,048.57	$1,048.65	$1,048.50