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	$129.85	8.496%	$140.8821	$140.88	$140.90	$140.90
Purchase #2	$129.28	3.366%	$133.6316	$133.63	$133.65	$133.60
Purchase #3	$161.50	6.795%	$172.4739	$172.47	$172.45	$172.50
Purchase #4	$35.64	13.299%	$40.3798	$40.38	$40.40	$40.40
Purchase #5	$63.78	12.714%	$71.889	$71.89	$71.90	$71.90
Purchase #6	$180.84	3.628%	$187.4009	$187.40	$187.40	$187.40
Purchase #7	$202.75	6.865%	$216.6688	$216.67	$216.65	$216.70
7 purchase totals =	$903.64		$963.3261	$963.32	$963.35	$963.40