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	$220.33	3.849%	$228.8105	$228.81	$228.80	$228.80
Purchase #2	$59.34	4.417%	$61.961	$61.96	$61.95	$62.00
Purchase #3	$81.97	5.219%	$86.248	$86.25	$86.25	$86.20
Purchase #4	$183.55	12.551%	$206.5874	$206.59	$206.60	$206.60
Purchase #5	$201.34	8.804%	$219.066	$219.07	$219.05	$219.10
Purchase #6	$114.82	7.815%	$123.7932	$123.79	$123.80	$123.80
Purchase #7	$59.79	13.447%	$67.83	$67.83	$67.85	$67.80
7 purchase totals =	$921.14		$994.2961	$994.30	$994.30	$994.30