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	$112.42	7.583%	$120.9448	$120.94	$120.95	$120.90
Purchase #2	$100.50	5.407%	$105.934	$105.93	$105.95	$105.90
Purchase #3	$18.25	13.865%	$20.7804	$20.78	$20.80	$20.80
Purchase #4	$194.53	9.680%	$213.3605	$213.36	$213.35	$213.40
Purchase #5	$12.76	3.447%	$13.1998	$13.20	$13.20	$13.20
Purchase #6	$133.66	6.560%	$142.4281	$142.43	$142.45	$142.40
Purchase #7	$30.73	9.501%	$33.6497	$33.65	$33.65	$33.60
7 purchase totals =	$602.85		$650.2973	$650.29	$650.35	$650.20