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	$45.33	13.645%	$51.5153	$51.52	$51.50	$51.50
Purchase #2	$111.54	3.463%	$115.4026	$115.40	$115.40	$115.40
Purchase #3	$40.40	13.806%	$45.9776	$45.98	$46.00	$46.00
Purchase #4	$215.46	5.676%	$227.6895	$227.69	$227.70	$227.70
Purchase #5	$22.58	13.228%	$25.5669	$25.57	$25.55	$25.60
Purchase #6	$74.27	6.223%	$78.8918	$78.89	$78.90	$78.90
Purchase #7	$232.46	5.256%	$244.6781	$244.68	$244.70	$244.70
7 purchase totals =	$742.04		$789.7218	$789.73	$789.75	$789.80