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	$194.70	11.199%	$216.5045	$216.50	$216.50	$216.50
Purchase #2	$82.34	9.377%	$90.061	$90.06	$90.05	$90.10
Purchase #3	$13.55	5.721%	$14.3252	$14.33	$14.35	$14.30
Purchase #4	$162.81	8.614%	$176.8345	$176.83	$176.85	$176.80
Purchase #5	$182.32	9.375%	$199.4125	$199.41	$199.40	$199.40
Purchase #6	$94.94	11.531%	$105.8875	$105.89	$105.90	$105.90
Purchase #7	$86.79	9.153%	$94.7339	$94.73	$94.75	$94.70
7 purchase totals =	$817.45		$897.7591	$897.75	$897.80	$897.70