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	$153.90	10.755%	$170.4519	$170.45	$170.45	$170.50
Purchase #2	$20.43	4.428%	$21.3346	$21.33	$21.35	$21.30
Purchase #3	$148.53	4.316%	$154.9406	$154.94	$154.95	$154.90
Purchase #4	$80.80	11.707%	$90.2593	$90.26	$90.25	$90.30
Purchase #5	$167.69	8.829%	$182.4954	$182.50	$182.50	$182.50
Purchase #6	$172.94	7.740%	$186.3256	$186.33	$186.35	$186.30
Purchase #7	$231.47	4.186%	$241.1593	$241.16	$241.15	$241.20
7 purchase totals =	$975.76		$1,046.9667	$1,046.97	$1,047.00	$1,047.00