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	$232.96	11.398%	$259.5128	$259.51	$259.50	$259.50
Purchase #2	$54.68	11.564%	$61.0032	$61.00	$61.00	$61.00
Purchase #3	$50.53	13.271%	$57.2358	$57.24	$57.25	$57.20
Purchase #4	$142.61	9.709%	$156.456	$156.46	$156.45	$156.50
Purchase #5	$88.66	3.259%	$91.5494	$91.55	$91.55	$91.50
Purchase #6	$131.51	10.165%	$144.878	$144.88	$144.90	$144.90
Purchase #7	$96.43	10.147%	$106.2148	$106.21	$106.20	$106.20
7 purchase totals =	$797.38		$876.8500	$876.85	$876.85	$876.80