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	$57.78	11.555%	$64.4565	$64.46	$64.45	$64.50
Purchase #2	$187.86	13.725%	$213.6438	$213.64	$213.65	$213.60
Purchase #3	$172.27	7.755%	$185.6295	$185.63	$185.65	$185.60
Purchase #4	$98.94	7.571%	$106.4307	$106.43	$106.45	$106.40
Purchase #5	$236.81	4.704%	$247.9495	$247.95	$247.95	$247.90
Purchase #6	$79.93	6.570%	$85.1814	$85.18	$85.20	$85.20
Purchase #7	$107.75	4.245%	$112.324	$112.32	$112.30	$112.30
7 purchase totals =	$941.34		$1,015.6154	$1,015.61	$1,015.65	$1,015.50