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	$120.56	9.348%	$131.8299	$131.83	$131.85	$131.80
Purchase #2	$171.60	6.588%	$182.905	$182.91	$182.90	$182.90
Purchase #3	$48.58	11.647%	$54.2381	$54.24	$54.25	$54.20
Purchase #4	$247.92	13.277%	$280.8363	$280.84	$280.85	$280.80
Purchase #5	$150.27	12.567%	$169.1544	$169.15	$169.15	$169.20
Purchase #6	$201.54	13.570%	$228.889	$228.89	$228.90	$228.90
Purchase #7	$192.80	8.700%	$209.5736	$209.57	$209.55	$209.60
7 purchase totals =	$1,133.27		$1,257.4263	$1,257.43	$1,257.45	$1,257.40