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	$168.84	10.361%	$186.3335	$186.33	$186.35	$186.30
Purchase #2	$195.34	11.775%	$218.3413	$218.34	$218.35	$218.30
Purchase #3	$222.27	6.372%	$236.433	$236.43	$236.45	$236.40
Purchase #4	$72.53	8.284%	$78.5384	$78.54	$78.55	$78.50
Purchase #5	$43.37	13.167%	$49.0805	$49.08	$49.10	$49.10
Purchase #6	$144.60	4.843%	$151.603	$151.60	$151.60	$151.60
Purchase #7	$75.88	13.107%	$85.8256	$85.83	$85.85	$85.80
7 purchase totals =	$922.83		$1,006.1553	$1,006.15	$1,006.25	$1,006.00