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	$192.85	4.181%	$200.9131	$200.91	$200.90	$200.90
Purchase #2	$80.82	12.521%	$90.9395	$90.94	$90.95	$90.90
Purchase #3	$118.42	11.322%	$131.8275	$131.83	$131.85	$131.80
Purchase #4	$180.47	4.215%	$188.0768	$188.08	$188.10	$188.10
Purchase #5	$58.65	7.723%	$63.1795	$63.18	$63.20	$63.20
Purchase #6	$119.87	13.526%	$136.0836	$136.08	$136.10	$136.10
Purchase #7	$174.91	10.111%	$192.5952	$192.60	$192.60	$192.60
7 purchase totals =	$925.99		$1,003.6152	$1,003.62	$1,003.70	$1,003.60