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	$196.44	11.111%	$218.2664	$218.27	$218.25	$218.30
Purchase #2	$208.35	13.452%	$236.3772	$236.38	$236.40	$236.40
Purchase #3	$13.67	6.663%	$14.5808	$14.58	$14.60	$14.60
Purchase #4	$98.32	10.820%	$108.9582	$108.96	$108.95	$109.00
Purchase #5	$76.32	9.396%	$83.491	$83.49	$83.50	$83.50
Purchase #6	$162.60	11.707%	$181.6356	$181.64	$181.65	$181.60
Purchase #7	$132.33	12.531%	$148.9123	$148.91	$148.90	$148.90
7 purchase totals =	$888.03		$992.2215	$992.23	$992.25	$992.30