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	$203.63	4.758%	$213.3187	$213.32	$213.30	$213.30
Purchase #2	$49.71	11.237%	$55.2959	$55.30	$55.30	$55.30
Purchase #3	$109.47	6.210%	$116.2681	$116.27	$116.25	$116.30
Purchase #4	$196.46	11.166%	$218.3967	$218.40	$218.40	$218.40
Purchase #5	$72.81	7.557%	$78.3123	$78.31	$78.30	$78.30
Purchase #6	$240.85	7.873%	$259.8121	$259.81	$259.80	$259.80
Purchase #7	$20.71	13.774%	$23.5626	$23.56	$23.55	$23.60
7 purchase totals =	$893.64		$964.9664	$964.97	$964.90	$965.00