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	$236.40	10.602%	$261.4631	$261.46	$261.45	$261.50
Purchase #2	$65.25	10.696%	$72.2291	$72.23	$72.25	$72.20
Purchase #3	$247.47	10.369%	$273.1302	$273.13	$273.15	$273.10
Purchase #4	$208.79	4.848%	$218.9121	$218.91	$218.90	$218.90
Purchase #5	$173.80	4.773%	$182.0955	$182.10	$182.10	$182.10
Purchase #6	$76.46	9.401%	$83.648	$83.65	$83.65	$83.60
Purchase #7	$8.66	3.648%	$8.9759	$8.98	$9.00	$9.00
7 purchase totals =	$1,016.83		$1,100.4539	$1,100.46	$1,100.50	$1,100.40