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	$187.82	11.311%	$209.0643	$209.06	$209.05	$209.10
Purchase #2	$95.80	8.175%	$103.6317	$103.63	$103.65	$103.60
Purchase #3	$59.62	13.156%	$67.4636	$67.46	$67.45	$67.50
Purchase #4	$245.51	13.550%	$278.7766	$278.78	$278.80	$278.80
Purchase #5	$113.58	8.755%	$123.5239	$123.52	$123.50	$123.50
Purchase #6	$190.47	4.718%	$199.4564	$199.46	$199.45	$199.50
Purchase #7	$197.78	11.662%	$220.8451	$220.85	$220.85	$220.80
7 purchase totals =	$1,090.58		$1,202.7616	$1,202.76	$1,202.75	$1,202.80