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	$87.73	3.455%	$90.7611	$90.76	$90.75	$90.80
Purchase #2	$189.98	12.356%	$213.4539	$213.45	$213.45	$213.50
Purchase #3	$90.89	7.197%	$97.4314	$97.43	$97.45	$97.40
Purchase #4	$11.44	9.620%	$12.5405	$12.54	$12.55	$12.50
Purchase #5	$161.81	11.804%	$180.9101	$180.91	$180.90	$180.90
Purchase #6	$36.25	11.561%	$40.4409	$40.44	$40.45	$40.40
Purchase #7	$54.86	3.532%	$56.7977	$56.80	$56.80	$56.80
7 purchase totals =	$632.96		$692.3356	$692.33	$692.35	$692.30