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	$95.62	10.828%	$105.9737	$105.97	$105.95	$106.00
Purchase #2	$66.73	8.852%	$72.6369	$72.64	$72.65	$72.60
Purchase #3	$223.84	12.162%	$251.0634	$251.06	$251.05	$251.10
Purchase #4	$73.88	10.214%	$81.4261	$81.43	$81.45	$81.40
Purchase #5	$8.28	3.164%	$8.542	$8.54	$8.55	$8.50
Purchase #6	$95.47	3.584%	$98.8916	$98.89	$98.90	$98.90
Purchase #7	$136.39	11.450%	$152.0067	$152.01	$152.00	$152.00
7 purchase totals =	$700.21		$770.5404	$770.54	$770.55	$770.50