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	$167.56	9.579%	$183.6106	$183.61	$183.60	$183.60
Purchase #2	$86.79	11.741%	$96.98	$96.98	$97.00	$97.00
Purchase #3	$62.42	12.108%	$69.9778	$69.98	$70.00	$70.00
Purchase #4	$43.86	4.381%	$45.7815	$45.78	$45.80	$45.80
Purchase #5	$137.56	3.664%	$142.6002	$142.60	$142.60	$142.60
Purchase #6	$62.91	7.155%	$67.4112	$67.41	$67.40	$67.40
Purchase #7	$183.37	13.451%	$208.0351	$208.04	$208.05	$208.00
7 purchase totals =	$744.47		$814.3964	$814.40	$814.45	$814.40