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	$165.41	10.367%	$182.5581	$182.56	$182.55	$182.60
Purchase #2	$221.43	7.836%	$238.7813	$238.78	$238.80	$238.80
Purchase #3	$179.63	12.714%	$202.4682	$202.47	$202.45	$202.50
Purchase #4	$166.31	9.304%	$181.7835	$181.78	$181.80	$181.80
Purchase #5	$61.54	7.191%	$65.9653	$65.97	$65.95	$66.00
Purchase #6	$124.61	12.449%	$140.1227	$140.12	$140.10	$140.10
Purchase #7	$92.97	8.156%	$100.5526	$100.55	$100.55	$100.60
7 purchase totals =	$1,011.90		$1,112.2317	$1,112.23	$1,112.20	$1,112.40