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	$158.62	6.409%	$168.786	$168.79	$168.80	$168.80
Purchase #2	$103.93	13.357%	$117.8119	$117.81	$117.80	$117.80
Purchase #3	$178.62	9.785%	$196.098	$196.10	$196.10	$196.10
Purchase #4	$60.65	11.226%	$67.4586	$67.46	$67.45	$67.50
Purchase #5	$201.61	13.288%	$228.3999	$228.40	$228.40	$228.40
Purchase #6	$38.56	5.225%	$40.5748	$40.57	$40.55	$40.60
Purchase #7	$82.37	7.396%	$88.4621	$88.46	$88.45	$88.50
7 purchase totals =	$824.36		$907.5913	$907.59	$907.55	$907.70