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	$161.65	3.570%	$167.4209	$167.42	$167.40	$167.40
Purchase #2	$112.74	9.648%	$123.6172	$123.62	$123.60	$123.60
Purchase #3	$188.30	5.630%	$198.9013	$198.90	$198.90	$198.90
Purchase #4	$40.58	12.498%	$45.6517	$45.65	$45.65	$45.70
Purchase #5	$117.71	6.582%	$125.4577	$125.46	$125.45	$125.50
Purchase #6	$200.67	7.377%	$215.4734	$215.47	$215.45	$215.50
Purchase #7	$193.96	8.261%	$209.983	$209.98	$210.00	$210.00
7 purchase totals =	$1,015.61		$1,086.5052	$1,086.50	$1,086.45	$1,086.60