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	$78.39	10.691%	$86.7707	$86.77	$86.75	$86.80
Purchase #2	$36.46	10.716%	$40.3671	$40.37	$40.35	$40.40
Purchase #3	$164.97	5.237%	$173.6095	$173.61	$173.60	$173.60
Purchase #4	$166.90	7.645%	$179.6595	$179.66	$179.65	$179.70
Purchase #5	$212.98	11.797%	$238.1053	$238.11	$238.10	$238.10
Purchase #6	$197.82	5.424%	$208.5498	$208.55	$208.55	$208.50
Purchase #7	$188.62	13.187%	$213.4933	$213.49	$213.50	$213.50
7 purchase totals =	$1,046.14		$1,140.5552	$1,140.56	$1,140.50	$1,140.60