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	$94.57	9.735%	$103.7764	$103.78	$103.80	$103.80
Purchase #2	$90.58	3.318%	$93.5854	$93.59	$93.60	$93.60
Purchase #3	$222.61	11.768%	$248.8067	$248.81	$248.80	$248.80
Purchase #4	$189.99	12.761%	$214.2346	$214.23	$214.25	$214.20
Purchase #5	$174.66	12.526%	$196.5379	$196.54	$196.55	$196.50
Purchase #6	$219.71	6.310%	$233.5737	$233.57	$233.55	$233.60
Purchase #7	$199.61	3.666%	$206.9277	$206.93	$206.95	$206.90
7 purchase totals =	$1,191.73		$1,297.4424	$1,297.45	$1,297.50	$1,297.40