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	$92.47	3.593%	$95.7924	$95.79	$95.80	$95.80
Purchase #2	$192.60	6.200%	$204.5412	$204.54	$204.55	$204.50
Purchase #3	$177.42	10.750%	$196.4927	$196.49	$196.50	$196.50
Purchase #4	$105.80	11.444%	$117.9078	$117.91	$117.90	$117.90
Purchase #5	$180.52	7.443%	$193.9561	$193.96	$193.95	$194.00
Purchase #6	$127.50	7.687%	$137.3009	$137.30	$137.30	$137.30
Purchase #7	$102.50	9.755%	$112.4989	$112.50	$112.50	$112.50
7 purchase totals =	$978.81		$1,058.4900	$1,058.49	$1,058.50	$1,058.50