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	$116.47	10.597%	$128.8123	$128.81	$128.80	$128.80
Purchase #2	$249.31	7.785%	$268.7188	$268.72	$268.70	$268.70
Purchase #3	$155.74	6.751%	$166.254	$166.25	$166.25	$166.30
Purchase #4	$103.59	8.586%	$112.4842	$112.48	$112.50	$112.50
Purchase #5	$106.74	9.178%	$116.5366	$116.54	$116.55	$116.50
Purchase #6	$94.45	3.430%	$97.6896	$97.69	$97.70	$97.70
Purchase #7	$228.46	3.781%	$237.0981	$237.10	$237.10	$237.10
7 purchase totals =	$1,054.76		$1,127.5936	$1,127.59	$1,127.60	$1,127.60