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	$194.77	5.735%	$205.9401	$205.94	$205.95	$205.90
Purchase #2	$99.96	7.410%	$107.367	$107.37	$107.35	$107.40
Purchase #3	$63.52	4.154%	$66.1586	$66.16	$66.15	$66.20
Purchase #4	$249.46	12.598%	$280.887	$280.89	$280.90	$280.90
Purchase #5	$136.65	3.384%	$141.2742	$141.27	$141.25	$141.30
Purchase #6	$242.44	13.394%	$274.9124	$274.91	$274.90	$274.90
Purchase #7	$109.47	4.159%	$114.0229	$114.02	$114.00	$114.00
7 purchase totals =	$1,096.27		$1,190.5622	$1,190.56	$1,190.50	$1,190.60