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	$148.88	13.172%	$168.4905	$168.49	$168.50	$168.50
Purchase #2	$170.38	6.547%	$181.5348	$181.53	$181.55	$181.50
Purchase #3	$58.81	11.265%	$65.4349	$65.43	$65.45	$65.40
Purchase #4	$78.39	6.221%	$83.2666	$83.27	$83.25	$83.30
Purchase #5	$90.29	3.268%	$93.2407	$93.24	$93.25	$93.20
Purchase #6	$96.52	7.654%	$103.9076	$103.91	$103.90	$103.90
Purchase #7	$218.47	13.833%	$248.691	$248.69	$248.70	$248.70
7 purchase totals =	$861.74		$944.5661	$944.56	$944.60	$944.50