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	$47.30	12.134%	$53.0394	$53.04	$53.05	$53.00
Purchase #2	$59.66	4.535%	$62.3656	$62.37	$62.35	$62.40
Purchase #3	$82.79	13.128%	$93.6587	$93.66	$93.65	$93.70
Purchase #4	$64.84	5.663%	$68.5119	$68.51	$68.50	$68.50
Purchase #5	$101.30	7.770%	$109.171	$109.17	$109.15	$109.20
Purchase #6	$89.81	12.192%	$100.7596	$100.76	$100.75	$100.80
Purchase #7	$150.69	9.351%	$164.781	$164.78	$164.80	$164.80
7 purchase totals =	$596.39		$652.2872	$652.29	$652.25	$652.40