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	$217.52	11.174%	$241.8257	$241.83	$241.85	$241.80
Purchase #2	$39.87	6.759%	$42.5648	$42.56	$42.55	$42.60
Purchase #3	$99.69	10.286%	$109.9441	$109.94	$109.95	$109.90
Purchase #4	$174.78	10.210%	$192.625	$192.63	$192.65	$192.60
Purchase #5	$30.38	9.557%	$33.2834	$33.28	$33.30	$33.30
Purchase #6	$157.33	6.374%	$167.3582	$167.36	$167.35	$167.40
Purchase #7	$246.92	10.146%	$271.9725	$271.97	$271.95	$272.00
7 purchase totals =	$966.49		$1,059.5737	$1,059.57	$1,059.60	$1,059.60