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	$85.46	8.297%	$92.5506	$92.55	$92.55	$92.60
Purchase #2	$222.55	7.121%	$238.3978	$238.40	$238.40	$238.40
Purchase #3	$203.92	13.170%	$230.7763	$230.78	$230.80	$230.80
Purchase #4	$19.63	11.646%	$21.9161	$21.92	$21.90	$21.90
Purchase #5	$173.36	7.618%	$186.5666	$186.57	$186.55	$186.60
Purchase #6	$116.90	9.301%	$127.7729	$127.77	$127.75	$127.80
Purchase #7	$175.49	7.700%	$189.0027	$189.00	$189.00	$189.00
7 purchase totals =	$997.31		$1,086.9830	$1,086.99	$1,086.95	$1,087.10