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	$100.43	5.388%	$105.8412	$105.84	$105.85	$105.80
Purchase #2	$138.67	8.256%	$150.1186	$150.12	$150.10	$150.10
Purchase #3	$168.91	11.507%	$188.3465	$188.35	$188.35	$188.30
Purchase #4	$233.40	9.525%	$255.6314	$255.63	$255.65	$255.60
Purchase #5	$189.37	13.818%	$215.5371	$215.54	$215.55	$215.50
Purchase #6	$155.89	13.308%	$176.6358	$176.64	$176.65	$176.60
Purchase #7	$82.93	4.441%	$86.6129	$86.61	$86.60	$86.60
7 purchase totals =	$1,069.60		$1,178.7235	$1,178.73	$1,178.75	$1,178.50