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	$127.79	10.669%	$141.4239	$141.42	$141.40	$141.40
Purchase #2	$190.75	4.264%	$198.8836	$198.88	$198.90	$198.90
Purchase #3	$128.64	12.555%	$144.7908	$144.79	$144.80	$144.80
Purchase #4	$33.62	12.750%	$37.9066	$37.91	$37.90	$37.90
Purchase #5	$193.47	9.356%	$211.5711	$211.57	$211.55	$211.60
Purchase #6	$213.55	5.778%	$225.8889	$225.89	$225.90	$225.90
Purchase #7	$153.64	11.583%	$171.4361	$171.44	$171.45	$171.40
7 purchase totals =	$1,041.46		$1,131.9010	$1,131.90	$1,131.90	$1,131.90