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	$159.83	7.422%	$171.6926	$171.69	$171.70	$171.70
Purchase #2	$175.87	12.844%	$198.4587	$198.46	$198.45	$198.50
Purchase #3	$84.84	6.806%	$90.6142	$90.61	$90.60	$90.60
Purchase #4	$37.40	10.734%	$41.4145	$41.41	$41.40	$41.40
Purchase #5	$123.55	8.167%	$133.6403	$133.64	$133.65	$133.60
Purchase #6	$52.95	6.814%	$56.558	$56.56	$56.55	$56.60
Purchase #7	$102.88	6.498%	$109.5651	$109.57	$109.55	$109.60
7 purchase totals =	$737.32		$801.9434	$801.94	$801.90	$802.00