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	$50.61	11.528%	$56.4443	$56.44	$56.45	$56.40
Purchase #2	$146.39	10.837%	$162.2543	$162.25	$162.25	$162.30
Purchase #3	$222.80	3.649%	$230.93	$230.93	$230.95	$230.90
Purchase #4	$167.29	12.182%	$187.6693	$187.67	$187.65	$187.70
Purchase #5	$249.79	11.511%	$278.5433	$278.54	$278.55	$278.50
Purchase #6	$58.77	4.523%	$61.4282	$61.43	$61.45	$61.40
Purchase #7	$196.46	13.285%	$222.5597	$222.56	$222.55	$222.60
7 purchase totals =	$1,092.11		$1,199.8291	$1,199.82	$1,199.85	$1,199.80