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	$213.39	13.194%	$241.5447	$241.54	$241.55	$241.50
Purchase #2	$249.33	7.238%	$267.3765	$267.38	$267.40	$267.40
Purchase #3	$209.53	11.382%	$233.3787	$233.38	$233.40	$233.40
Purchase #4	$95.74	5.741%	$101.2364	$101.24	$101.25	$101.20
Purchase #5	$217.35	7.501%	$233.6534	$233.65	$233.65	$233.70
Purchase #6	$112.56	12.851%	$127.0251	$127.03	$127.05	$127.00
Purchase #7	$205.74	9.290%	$224.8532	$224.85	$224.85	$224.90
7 purchase totals =	$1,303.64		$1,429.0680	$1,429.07	$1,429.15	$1,429.10