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	$241.87	10.609%	$267.53	$267.53	$267.55	$267.50
Purchase #2	$28.38	10.665%	$31.4067	$31.41	$31.40	$31.40
Purchase #3	$146.58	12.489%	$164.8864	$164.89	$164.90	$164.90
Purchase #4	$17.82	4.303%	$18.5868	$18.59	$18.60	$18.60
Purchase #5	$196.69	11.184%	$218.6878	$218.69	$218.70	$218.70
Purchase #6	$115.53	6.652%	$123.2151	$123.22	$123.20	$123.20
Purchase #7	$53.27	4.736%	$55.7929	$55.79	$55.80	$55.80
7 purchase totals =	$800.14		$880.1057	$880.12	$880.15	$880.10