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	$166.91	3.401%	$172.5866	$172.59	$172.60	$172.60
Purchase #2	$199.72	6.815%	$213.3309	$213.33	$213.35	$213.30
Purchase #3	$97.72	6.323%	$103.8988	$103.90	$103.90	$103.90
Purchase #4	$116.52	6.834%	$124.483	$124.48	$124.50	$124.50
Purchase #5	$214.31	9.824%	$235.3638	$235.36	$235.35	$235.40
Purchase #6	$117.73	10.790%	$130.4331	$130.43	$130.45	$130.40
Purchase #7	$162.67	8.418%	$176.3636	$176.36	$176.35	$176.40
7 purchase totals =	$1,075.58		$1,156.4598	$1,156.45	$1,156.50	$1,156.50