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	$128.54	11.119%	$142.8324	$142.83	$142.85	$142.80
Purchase #2	$70.33	8.786%	$76.5092	$76.51	$76.50	$76.50
Purchase #3	$96.26	13.508%	$109.2628	$109.26	$109.25	$109.30
Purchase #4	$61.30	8.561%	$66.5479	$66.55	$66.55	$66.50
Purchase #5	$245.82	5.577%	$259.5294	$259.53	$259.55	$259.50
Purchase #6	$143.79	8.241%	$155.6397	$155.64	$155.65	$155.60
Purchase #7	$125.96	10.400%	$139.0598	$139.06	$139.05	$139.10
7 purchase totals =	$872.00		$949.3812	$949.38	$949.40	$949.30