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	$136.56	3.719%	$141.6387	$141.64	$141.65	$141.60
Purchase #2	$119.63	9.135%	$130.5582	$130.56	$130.55	$130.60
Purchase #3	$147.31	11.842%	$164.7545	$164.75	$164.75	$164.80
Purchase #4	$185.66	7.189%	$199.0071	$199.01	$199.00	$199.00
Purchase #5	$106.47	6.812%	$113.7227	$113.72	$113.70	$113.70
Purchase #6	$146.53	5.355%	$154.3767	$154.38	$154.40	$154.40
Purchase #7	$81.53	10.808%	$90.3418	$90.34	$90.35	$90.30
7 purchase totals =	$923.69		$994.3997	$994.40	$994.40	$994.40