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	$202.63	9.618%	$222.119	$222.12	$222.10	$222.10
Purchase #2	$56.47	5.686%	$59.6809	$59.68	$59.70	$59.70
Purchase #3	$125.52	12.689%	$141.4472	$141.45	$141.45	$141.40
Purchase #4	$15.96	6.645%	$17.0205	$17.02	$17.00	$17.00
Purchase #5	$41.45	13.804%	$47.1718	$47.17	$47.15	$47.20
Purchase #6	$64.72	11.513%	$72.1712	$72.17	$72.15	$72.20
Purchase #7	$48.94	5.809%	$51.7829	$51.78	$51.80	$51.80
7 purchase totals =	$555.69		$611.3935	$611.39	$611.35	$611.40