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	$85.52	10.500%	$94.4996	$94.50	$94.50	$94.50
Purchase #2	$127.25	12.856%	$143.6093	$143.61	$143.60	$143.60
Purchase #3	$76.80	11.356%	$85.5214	$85.52	$85.50	$85.50
Purchase #4	$103.46	5.779%	$109.439	$109.44	$109.45	$109.40
Purchase #5	$9.69	7.423%	$10.4093	$10.41	$10.40	$10.40
Purchase #6	$188.48	13.849%	$214.5826	$214.58	$214.60	$214.60
Purchase #7	$103.31	11.866%	$115.5688	$115.57	$115.55	$115.60
7 purchase totals =	$694.51		$773.6300	$773.63	$773.60	$773.60