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	$166.46	6.130%	$176.664	$176.66	$176.65	$176.70
Purchase #2	$173.43	6.810%	$185.2406	$185.24	$185.25	$185.20
Purchase #3	$239.53	9.765%	$262.9201	$262.92	$262.90	$262.90
Purchase #4	$234.67	12.864%	$264.8579	$264.86	$264.85	$264.90
Purchase #5	$78.48	5.581%	$82.86	$82.86	$82.85	$82.90
Purchase #6	$7.44	12.693%	$8.3844	$8.38	$8.40	$8.40
Purchase #7	$14.30	4.391%	$14.9279	$14.93	$14.95	$14.90
7 purchase totals =	$914.31		$995.8549	$995.85	$995.85	$995.90