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	$147.66	11.770%	$165.0396	$165.04	$165.05	$165.00
Purchase #2	$250.57	12.523%	$281.9489	$281.95	$281.95	$281.90
Purchase #3	$77.65	3.586%	$80.4345	$80.43	$80.45	$80.40
Purchase #4	$196.38	13.522%	$222.9345	$222.93	$222.95	$222.90
Purchase #5	$187.73	9.549%	$205.6563	$205.66	$205.65	$205.70
Purchase #6	$49.32	8.393%	$53.4594	$53.46	$53.45	$53.50
Purchase #7	$91.77	4.139%	$95.5684	$95.57	$95.55	$95.60
7 purchase totals =	$1,001.08		$1,105.0416	$1,105.04	$1,105.05	$1,105.00