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	$44.63	10.840%	$49.4679	$49.47	$49.45	$49.50
Purchase #2	$176.61	5.474%	$186.2776	$186.28	$186.30	$186.30
Purchase #3	$245.79	12.266%	$275.9386	$275.94	$275.95	$275.90
Purchase #4	$80.99	11.431%	$90.248	$90.25	$90.25	$90.20
Purchase #5	$141.55	4.660%	$148.1462	$148.15	$148.15	$148.10
Purchase #6	$83.44	3.486%	$86.3487	$86.35	$86.35	$86.30
Purchase #7	$172.41	5.275%	$181.5046	$181.50	$181.50	$181.50
7 purchase totals =	$945.42		$1,017.9316	$1,017.94	$1,017.95	$1,017.80