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	$117.83	7.674%	$126.8723	$126.87	$126.85	$126.90
Purchase #2	$215.25	11.715%	$240.4665	$240.47	$240.45	$240.50
Purchase #3	$148.75	9.255%	$162.5168	$162.52	$162.50	$162.50
Purchase #4	$170.33	13.204%	$192.8204	$192.82	$192.80	$192.80
Purchase #5	$26.39	8.491%	$28.6308	$28.63	$28.65	$28.60
Purchase #6	$215.36	9.638%	$236.1164	$236.12	$236.10	$236.10
Purchase #7	$115.64	7.677%	$124.5177	$124.52	$124.50	$124.50
7 purchase totals =	$1,009.55		$1,111.9409	$1,111.95	$1,111.85	$1,111.90