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	$123.34	3.418%	$127.5558	$127.56	$127.55	$127.60
Purchase #2	$150.46	12.197%	$168.8116	$168.81	$168.80	$168.80
Purchase #3	$37.85	6.861%	$40.4469	$40.45	$40.45	$40.40
Purchase #4	$181.77	4.167%	$189.3444	$189.34	$189.35	$189.30
Purchase #5	$146.25	13.299%	$165.6998	$165.70	$165.70	$165.70
Purchase #6	$249.45	7.354%	$267.7946	$267.79	$267.80	$267.80
Purchase #7	$182.80	8.121%	$197.6452	$197.65	$197.65	$197.60
7 purchase totals =	$1,071.92		$1,157.2983	$1,157.30	$1,157.30	$1,157.20