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	$83.41	3.188%	$86.0691	$86.07	$86.05	$86.10
Purchase #2	$78.67	8.387%	$85.2681	$85.27	$85.25	$85.30
Purchase #3	$93.29	3.255%	$96.3266	$96.33	$96.35	$96.30
Purchase #4	$166.41	9.245%	$181.7946	$181.79	$181.80	$181.80
Purchase #5	$69.91	4.242%	$72.8756	$72.88	$72.90	$72.90
Purchase #6	$74.30	5.141%	$78.1198	$78.12	$78.10	$78.10
Purchase #7	$66.42	4.184%	$69.199	$69.20	$69.20	$69.20
7 purchase totals =	$632.41		$669.6528	$669.66	$669.65	$669.70