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	$57.40	7.404%	$61.6499	$61.65	$61.65	$61.60
Purchase #2	$195.91	11.754%	$218.9373	$218.94	$218.95	$218.90
Purchase #3	$123.53	7.319%	$132.5712	$132.57	$132.55	$132.60
Purchase #4	$40.92	3.132%	$42.2016	$42.20	$42.20	$42.20
Purchase #5	$247.84	3.266%	$255.9345	$255.93	$255.95	$255.90
Purchase #6	$245.29	11.209%	$272.7846	$272.78	$272.80	$272.80
Purchase #7	$76.82	7.848%	$82.8488	$82.85	$82.85	$82.80
7 purchase totals =	$987.71		$1,066.9279	$1,066.92	$1,066.95	$1,066.80