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	$203.95	13.544%	$231.573	$231.57	$231.55	$231.60
Purchase #2	$237.56	11.508%	$264.8984	$264.90	$264.90	$264.90
Purchase #3	$125.76	13.207%	$142.3691	$142.37	$142.35	$142.40
Purchase #4	$9.64	6.719%	$10.2877	$10.29	$10.30	$10.30
Purchase #5	$119.73	6.445%	$127.4466	$127.45	$127.45	$127.40
Purchase #6	$146.60	4.515%	$153.219	$153.22	$153.20	$153.20
Purchase #7	$148.64	10.863%	$164.7868	$164.79	$164.80	$164.80
7 purchase totals =	$991.88		$1,094.5806	$1,094.59	$1,094.55	$1,094.60