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	$121.90	4.694%	$127.622	$127.62	$127.60	$127.60
Purchase #2	$30.31	4.149%	$31.5676	$31.57	$31.55	$31.60
Purchase #3	$88.63	10.667%	$98.0842	$98.08	$98.10	$98.10
Purchase #4	$37.91	11.695%	$42.3436	$42.34	$42.35	$42.30
Purchase #5	$29.41	4.461%	$30.722	$30.72	$30.70	$30.70
Purchase #6	$181.49	7.340%	$194.8114	$194.81	$194.80	$194.80
Purchase #7	$237.27	10.600%	$262.4206	$262.42	$262.40	$262.40
7 purchase totals =	$726.92		$787.5714	$787.56	$787.50	$787.50