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	$176.33	6.531%	$187.8461	$187.85	$187.85	$187.80
Purchase #2	$83.54	8.271%	$90.4496	$90.45	$90.45	$90.40
Purchase #3	$113.65	9.642%	$124.6081	$124.61	$124.60	$124.60
Purchase #4	$208.53	5.767%	$220.5559	$220.56	$220.55	$220.60
Purchase #5	$238.87	10.235%	$263.3183	$263.32	$263.30	$263.30
Purchase #6	$71.33	10.227%	$78.6249	$78.62	$78.60	$78.60
Purchase #7	$246.68	7.616%	$265.4671	$265.47	$265.45	$265.50
7 purchase totals =	$1,138.93		$1,230.8700	$1,230.88	$1,230.80	$1,230.80