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	$78.79	4.662%	$82.4632	$82.46	$82.45	$82.50
Purchase #2	$171.82	4.158%	$178.9643	$178.96	$178.95	$179.00
Purchase #3	$64.92	11.444%	$72.3494	$72.35	$72.35	$72.30
Purchase #4	$53.54	9.136%	$58.4314	$58.43	$58.45	$58.40
Purchase #5	$123.60	10.271%	$136.295	$136.30	$136.30	$136.30
Purchase #6	$105.97	6.560%	$112.9216	$112.92	$112.90	$112.90
Purchase #7	$78.57	6.115%	$83.3746	$83.37	$83.35	$83.40
7 purchase totals =	$677.21		$724.7995	$724.79	$724.75	$724.80