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	$177.87	7.864%	$191.8577	$191.86	$191.85	$191.90
Purchase #2	$164.71	4.599%	$172.285	$172.29	$172.30	$172.30
Purchase #3	$146.95	10.756%	$162.7559	$162.76	$162.75	$162.80
Purchase #4	$52.69	3.290%	$54.4235	$54.42	$54.40	$54.40
Purchase #5	$93.33	12.296%	$104.8059	$104.81	$104.80	$104.80
Purchase #6	$218.38	9.525%	$239.1807	$239.18	$239.20	$239.20
Purchase #7	$115.87	10.546%	$128.0897	$128.09	$128.10	$128.10
7 purchase totals =	$969.80		$1,053.3984	$1,053.41	$1,053.40	$1,053.50