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	$177.59	8.312%	$192.3513	$192.35	$192.35	$192.40
Purchase #2	$31.58	7.223%	$33.861	$33.86	$33.85	$33.90
Purchase #3	$162.96	5.778%	$172.3758	$172.38	$172.40	$172.40
Purchase #4	$177.43	3.305%	$183.2941	$183.29	$183.30	$183.30
Purchase #5	$51.69	5.467%	$54.5159	$54.52	$54.50	$54.50
Purchase #6	$250.56	3.642%	$259.6854	$259.69	$259.70	$259.70
Purchase #7	$41.87	4.208%	$43.6319	$43.63	$43.65	$43.60
7 purchase totals =	$893.68		$939.7154	$939.72	$939.75	$939.80