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	$76.77	8.226%	$83.0851	$83.09	$83.10	$83.10
Purchase #2	$117.92	8.152%	$127.5328	$127.53	$127.55	$127.50
Purchase #3	$197.26	5.355%	$207.8233	$207.82	$207.80	$207.80
Purchase #4	$115.47	10.700%	$127.8253	$127.83	$127.85	$127.80
Purchase #5	$123.40	13.817%	$140.4502	$140.45	$140.45	$140.50
Purchase #6	$73.94	12.197%	$82.9585	$82.96	$82.95	$83.00
Purchase #7	$172.77	12.118%	$193.7063	$193.71	$193.70	$193.70
7 purchase totals =	$877.53		$963.3815	$963.39	$963.40	$963.40