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	$178.38	4.504%	$186.4142	$186.41	$186.40	$186.40
Purchase #2	$202.81	4.310%	$211.5511	$211.55	$211.55	$211.60
Purchase #3	$72.75	13.430%	$82.5203	$82.52	$82.50	$82.50
Purchase #4	$109.91	8.590%	$119.3513	$119.35	$119.35	$119.40
Purchase #5	$126.44	11.573%	$141.0729	$141.07	$141.05	$141.10
Purchase #6	$179.74	8.161%	$194.4086	$194.41	$194.40	$194.40
Purchase #7	$113.52	8.688%	$123.3826	$123.38	$123.40	$123.40
7 purchase totals =	$983.55		$1,058.7010	$1,058.69	$1,058.65	$1,058.80